Most relationships fail period!
If they did not we'd all be married to our high school sweethearts! If you throw in (youth) and (mental illness) you're not exactly increasing the odds of having a lifelong relationship. The majority of people seek out mates with the (least) amount of "baggage". All love and relationships are a calculated gamble.
You have to really know (yourself) before you select a mate. Only you know what you want in a mate. Keep in mind people want to be loved and appreciated for who they are. Therefore you don't want to be with someone hoping they'll change.
There are only two ways to experience joy and peace of mind in relationships. We either get what we want or we learn to be happy with what we have.
Best of luck!