Is it Worth it---Not Fiction, from my heart

Are some things worth the trouble and hurt they put you through? And of course referring relationships. You seem happy at first but then all of a sudden the beginning facades disappear and it seems as if you are staring an ugly monster in the face. Now the truth is revealed but you want to keep that, "I'm in it to win it" idea in your head and not give up so easily. But my question is, if negative things continue to happen and you have more sad days than happy days, then is it even worth it anymore? You wanna say, ok it's a phase and things will get better, but next thing you know it's a year later and things are still the same. I played this with my ex, and it was time wasted I think. If I knew at the beginning of that relationship what I knew at the end then I would have left months earlier, but that's life. Now I feel in the same predicament again. I wanna stick around, see if things get better and not miss out on a good opportunity, but on the other hand I don't want to waste time on something that may not be worth it. I was so much happier single than I am now in a relationship. I never said I wanted a relationship, it just snuck up on me, and maybe I wasn't ready for this. I don't want to do this anymore. Am I being selfish, only thinking about my self -happiness? Or if I'm even considering getting out is that a sign I should? Confused a bit, but I think I know my answer.