Does it ever happen that two people with personal problems get married with the idea of providing mutual support?

There are plenty of cases where one person in a marriage has personal problems and such relationships tend to be unstable because one person places too many demands on the other.

But what if two people with problems enter into a marriage, each acknowledging personal problems as well as those of the partner. They form a pact to be tolerant of the other’s short comings and to be supportive.
My suspicion is that this is a romantic fantasy on my part and that such marriages rarely if ever occur and, when they do, are not very long lasting.