Love affairs almost always begin with, "I'll stay as long as," commitments. "I'll stay as long as love is happening," "I'll stay as long as it feels right," "I'll stay as long as my needs are being met," etc.
This is normal and healthy, and most relationships end before people spend a lifetime together, or even a significant number of months and years together. Relationships that end aren't necessarily failures. They are often successful relationships that ran their course and people moved on--hopefully wiser and more able to love better in the future.
If we feel that we want a life partnership with a person, the commitment needs to shift from, "I'll stay as long as," to "I'll do what it takes to make us work." This is a massive change in commitment!
"I'll do what it takes," means that when problems occur (as they always do because all intimacy involves suffering to some extent), we don't waste time separating, debating with ourselves whether we should stay or not, or tolerating unacceptable behavior in the hopes that we'll somehow escape it eventually.
"I'll do what it takes," commitments mean that problems are recognized and addressed with the understanding that our job is to get back to love. It is not a matter of whether we should do the work required, or are even able to do it. Our job is to do what it takes! We need to address problems, solve them into satisfying intimacy, and, if we can't solve them, get help and learn how to love each other better.
Couples who marry, create families, and unconsciously hold on to, "I'll stay as long as," commitments are less likely to recognize problems, take responsibility for them, and resolve them into deeper love. When such couples fight, one or both often unconsciously shift into, "I'll stay as long as," internally debating whether to stay or go, which blocks addressing the urgent problems that are happening right now!
If you are in a relationship, check out your commitments. Are you in the first relational stages of, "I'll stay as long as," or have you shifted into, "I'll do what it takes," mode? Talk about it with your partner, and, if problems arise from your conversation which don't resolve into deeper intimacy, go talk with a therapist you both like.