You have to have your own lives outside of the relationship as well. It cant just be about the couple.
I am learning something similar, too. I have a particularly hard time accepting that long term relationships have ups and downs, and I always feel so distressed during a difficult period because in my mind, it'll always be this way, it's a downhill spiral, and it's just going to be terrible from here on out. It's like my mind can't comprehend the fact that things CAN get better. I'm slowly (and painfully) teaching myself to realize that relationships are dynamic, and have normal ebbs and flows. Acceptance of that process will only make it easier.It's really helped me to learn how to look at the relationship more like a marathon instead of a sprint. It used to really upset and scare me when I would feel like I didn't want to be around my partner after a disagreement or if I was in a particularly bad mood. Over time I've begun to understand how to just disengage and delve into some kind of activity when I'm annoyed at my husband. Inevitably a few hours later I'll start feeling lovey towards him again. It's just not a big deal.