I'm definitely not condemning you for having personal experience with mental illness or feeling comfortable bringing it up in your essay. I hope that's not how it came across.
I was just told that, like knp said, you don't want it to seem like you're getting into the program to learn about yourself. And it can seem as if "you're interested in this now because it's directly affecting your life right now but what about 15 years down the line when it's possibly not so relevant?" (I'm not meaning to imply mental illness always gets better with time, I'm aware it doesn't. Just setting up a hypothetical).