In his first public remarks since leaving the company he co-founded, Kevin Systrom hinted at tensions with Facebook that could have hastened his exit from Instagram. But he also said “there are no hard feelings at all” and that he would continue rooting for the company as he moves on to work on other projects.

“When you leave anything, there are obviously reasons for leaving,” Systrom told interviewer Lauren Goode onstage at Monday’s Wired 25 conference. “No one ever leaves a job because everything’s awesome, right? Work’s hard.”

At the same time, Systrom noted that he and co-founder Mike Krieger had stayed at Instagram six years after they sold their company to Facebook for $1 billion — which is far longer than most entrepreneurs stay after selling their companies.

Systrom and Krieger abruptly resigned from Instagram on September 24th. Their exit has been widely viewed as the end of Instagram’s pseudo-independence from its parent company.

Systrom and Krieger left Instagram at a time when it is more important to Facebook’s future than ever. With the number of young people using Facebook daily in decline, the company will increasingly turn toward Instagram to build its future.

In a farewell post, Systrom all but promised to start another company. He told Goode that he and Krieger would likely work together again, but he had no time frame for starting a new company. He said he wanted to spend the next several months working on being a good father to his nine-month-old daughter and exploring his creativity and other hobbies. (He has recently taken up flying.)

Systrom said he was confident that Instagram would continue to be successful even without its co-founders at the helm. “I want this thing to succeed,” Systrom said. “If this thing triples in size and becomes the most important thing in the world, that would be an awesome outcome for me, even if i’m not running it.”

Still, the mystery of why the co-founders resigned when they did remains. Systrom dodged a question from Goode about what it felt like to tell Facebook CEO Mark Zuckerberg that he was leaving, except to say that he had a mixture of emotions. But in a sign of how abruptly the decision was made, he said that he had written that farewell post “very, very quickly.”