My longest relationship began seven years ago. I think I can say that I’ve been a dedicated partner. Like any relationship, we’ve had our fair share of ups and downs. There have been times that felt like nothing could possibly come between us. Then there have been times that felt so dark I thought the only choice we had was to go our separate ways. For better or worse, we have always found our way back to one another. This love is addictive and all-encompassing. This love I’m referring to is my long-term, codependent relationship with Instagram.

There were others before Instagram. Myspace was my first, then a moment with Facebook and a liaison with Twitter. I was cutting my teeth, learning how to communicate with the world beyond me. When Instagram rolled in, I was ready for the long-term. I loved that it was image-focussed; having worked as a model for most of my life, I knew how to make something look desirable.

When I joined the site in 2012, the affair was a casual one. I recently scrolled all the way back to the beginning, more than 4,000 posts ago. The first photos were so sweet, so innocent and so naive: heavily filtered “fun” breakfasts I made for my then boyfriend, screenshots of texts between my sister and me about J-Lo, and photos of random cats I found under people’s cars.

Since then, Instagram has become the overall facilitator of life, a hub to find work, friends, romantic relationships and holiday destinations.

When my body changed as I hit my early 20s, I found myself at a very average UK size 12 – and no longer skinny enough to model for “normal” brands. Modelling is a job where every day your role is to be a different version of yourself – the version a brand or client wants you to be. But now it felt as if the world didn’t want me to be anything. I scanned TV, movies and magazines and realised that it was rare to see a woman who wasn’t sample size. So Instagram became the place where I could channel my frustration with narrow-minded perspectives on beauty by posting the kinds of images I wanted to see in the world.

In 2015, then at a UK size 14/16, I posted a photo of myself on the beach in Brazil in a tiny string bikini. My hair was wet from the ocean and I was drinking a cold beer and laughing because, at that moment, I felt so free. Now everyone is posting this sort of thing – but, at the time, seeing a body like mine in a swimsuit was radical. Those beach shots became a BBC headline (“Naomi Shimada on Body Positivity and Bikinis”).

Soon, my photos – sometimes nude, sometimes dressed in rainbow-hued outfits – were re-posted countless times, and my follower count started to shoot up. My inbox would be full to the brim with touching messages from other women who wanted to see themselves reflected in the media. I remember the high I felt – and I began to believe I was on to something, that a shift was starting to happen in the world; a shift where people wanted to see different kinds of approaches to beauty and living.

Posting shots of a body like mine in a swimsuit was radical

But this sweet honeymoon stage soon came crashing down. Last year I had a wake-up call on the effect social media was having on my state of mind when I went through a period of acute anxiety and struggled to function for months. My love affair with Instagram and my new sense of self had turned ugly. Eventually, the idea of performing on the platform when I didn’t want to trigger such deep feelings that even fulfilling the smallest of tasks – from getting to my dance class to doing my weekly shop – felt daunting.

It turns out I was a statistic. A study published in the journal JAMA Psychiatry in September found that of 6,600 young people, those who spent more than three hours a day on social media were more likely to develop mental health problems, including anxiety and depression.

As Instagram exploded, becoming a platform for celebrity as well as political and social influence, everything on my feed suddenly seemed to need to become more veneered – and more self-promotional. The app had become a workspace where we were supposed to put only our best foot forward.

As my follower numbers increased and I started to earn money from sponsored posts, the innocence of how I used the app began to get lost. I was left thinking: are we the ones evolving these apps or are these apps changing us?

As my success with it increased, so did the weight of responsibility. What do you lose when you start commodifying your essence and your authenticity? Do you become less you? I became increasingly aware that happiness on social media is intertwined with capitalistic ideals of success. Is this what I actually wanted, or was this an ideal I had absorbed from social media’s societal messaging? I was getting lost in the culture of comparison that apps like Instagram create.

I was forced to seriously question these ideals when I found myself in an actual romantic relationship with someone who I met on Instagram. By swiftly examining his profile I decided he ticked all of what I thought were my “boxes”. My spy-like examination of his page told me he was smart, beautiful and that we had many similar interests. When we eventually started to speak via DMs, our conversations flowed easily. My physical reactions to our digital interactions were strong. I was hooked.

My human complexity isn’t decided on by a wall of square images

There were knots in my stomach, butterflies and giddy excitement. I quickly started to fantasise what a future together could look like for us. Meeting in real life was intoxicating. A digital fantasy had, seemingly, become reality. Our relationship moved quickly because we were both in love with another image, the one we’d created of the other person – an image that was almost purely based on each other’s social media profiles.

And so, just as quickly as it started, things swiftly took a downward spiral as we woke up to the reality, rather than the perfect avatar versions, of each other. The work, holiday and family photos that had made me feel so drawn to him, were not, of course, all that he was: there was a huge amount of complexity beneath those images. For both of us, our behaviour and the reality of who we were didn’t match up to the other’s expectations, which led to us breaking up.

While writing a book about our relationship with social media, I realised it was exactly that: a relationship. And I needed to treat it like one. For it to be healthy and functional, I needed boundaries, I needed breaks, I needed room to breathe. And I needed to set my own expectations.

Still, the thought of completely stepping away from social media is unimaginable. I think I would feel very lost. After all, it’s how I’ve met some of my best friends. It’s also my biggest resource for being able to see things from different perspectives. I still want to be a person of the digital world, but I needed to take into account that apps like Instagram want to keep me hooked.

By taking breaks and choosing when to be online, I’ve found that there is a richness in the quiet, a secret symphony in airplane mode. Having learned that, I am now hopeful that I can continue to be a part of sharing and creating the world I want to see and be a part of.

The most important lesson has been to realise that my self-worth is not based on a number – of followers or likes. Whatever I achieve or accomplish is not what makes me worthy as a person. My abundant human complexity is not determined by a tiled wall of square images and nor is it dependent on external validation. I still believe in goals, it’s just that the goals look very different now. Just because something looks good doesn’t mean it is good, so I’m going to keep making decisions based on how things feel over how they look. I feel rich in love, connection and experience and while Instagram has at times facilitated some of these things, deep down I know that I am the source of that richness – and no app can ever take my place.

Mixed Feelings: Exploring the Emotional Impact of our Digital Habits by Naomi Shimada and Sarah Raphael is published by Quadrille at £16.99. Buy it for £14.95 at guardianbookshop.com

Makeup by Celia Evans at One Represents using Cutie Pie; hair by Tommy Stayton; jumpsuit by Issey Miyake Pleats Please; Jewellery by Alighieri