Obviously no rule is absolute and every person is unique, but I've noticed that people who have been mentally ill since childhood often have a different relationship to their illnesses than those who developed them as adults.
I developed bipolar by age five, meaning that I literally don't have any memories of having "normal" emotions. Bipolar has been part of my identity for as long as I've had one, so I integrated it into my life and learned to adapt. Honestly, if you went back in time and prevented me from developing it, you would end up with a totally different person today - a happier one, sure, but ultimately not me. None of the people I know who developed bipolar as adults feel this way; nor, for that matter, do I feel like this about the psychosis I developed in my early twenties. (On the other hand, if I could make some quick genetic edits that would prevent my kids from developing mood disorders and do nothing else, I would.)