Committing to sticking through things doesn't automatically mean there's no pain, or that the pain experienced by staying together won't exceed the pain of ending the relationship. The idea that marriage is for life is just a social and religious idea, and then a fairly recent one. There's no natural law that states that it is, or even should be, for life. If you're not happy in a relationship, whatever its stage, and have little belief that anything can be done to make you happy, then end it. Not saying it's easy, but I daresay it'll be worthwhile in the long run.