Couples who fight all the time aren't being healthy, "staying with [each other] no matter what!" Sometimes staying together isn't healthy. That's not what love is. It can be dependency.

Staying together through thick and thin means staying even when there's problems, but it's not all about fighting problems. Too much fighting is no good. The problems a strong couple sticks together through includes health problems, problems from outside sources, even cheating (but staying together through lots of cheating, IMO, is only enabling the other to cheat). But just because a couple stays together, doesn't mean they love each other and they have a healthy relationship. Some relationships are poisonous, but they stay together, anyway.