Toni Antonucci, Kristine Ajrouch, and Noah Webster wrote a piece in The Conversation about their research on what traits make a relationship more likely to endure:

In a recent study, we found that one trait in particular – humility – is an important indicator of successful relationships…If you're humble, you lack a host of negative qualities, such as arrogance and overconfidence. It means you can acknowledge mistakes, see value in things that are riddled with imperfections and identify areas for improvement.