Livre d'Or

I suspect that some people find it easier not to frame a break-up as due to adversity, at least when talking to other people, because there are strong expectations to stick with a partner through tough times. Very few people are going to say "I left my partner because they became disabled," but they might say "because they changed too much" or "because they were demanding too much of me." And sometimes those stresses—things like serious health issues or poverty—cause ongoing arguments or worse, but there's no way of knowing ahead of time which of our partners will stick around for disability, or which of us will take out stress on the people we love.

I can't see myself making a long-term commitment to someone with seriously incompatible life goals (though, as you note, goals can change).

Also, "start with the right people" is probably true, but I find myself wishing for some sort of education in identifying who the right people are for a given person. (Someone could be absolutely wonderful, but want a partner to help them raise children, or want monogamy, either of which would mean they could be my good friend but not my life partner.)