After losing an incredible 350 lbs., Jacqueline Adan felt nervous — but ready — to wear a bathing suit for the first time on vacation in Mexico.

“For a brief moment, I thought to myself, ‘I can’t do this. I can’t take this cover-up off,’ ” Adan, 30, tells PEOPLE. “It took a lot for me to actually tell myself, ‘It’s OK, you are beautiful just the way you are.’ ”

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But the moment she faced her fears and bared her body, a couple nearby started pointing and laughing at her loose skin.

“I did not know if I was going to cry or put my cover-up back on and not go swimming. For a moment I froze,” Adan says. “I could not believe how someone could judge me and make fun of me. They had no idea who I was, what I had been through or what I was currently going through.”

Adan says that if the incident had happened before she had lost weight, when she was “embarrassed and ashamed” of how she looked, she likely would’ve covered up and run back to her room to cry.

“I would have allowed their comments to affect my vacation and I probably would not have gone to the beach or pool again,” Adan says.

But after three years of tough work to drastically slim down — thanks to a healthy diet and exercise — Adan decided she’d earned the right to strut down to the water.

“That’s when it hit me … they have no idea about my weight loss, so why am I going to let their opinions affect me? How I feel about myself is what matters,” she says. “And so that’s exactly why I smiled at them and jumped into the pool!”

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Adan, a preschool teacher in San Francisco who also writes a blog to document her weight loss journey, shared her story on Instagram, where it quickly went viral.

Image zoom Jacqueline Adan/Instagram

“Knowing that it has reached so many people, and that I am getting so many comments and messages of people telling me how much this post has helped them truly means the world to me!” she says. “I want people to know that if I can feel confident and beautiful in my body, with lots of loose skin, even after losing 350 lbs., then I hope they can focus on who they are and forget everyone else who tries to bring them down!”

And Adan wants to encourage other people on their weight loss journeys to keep going.