This one's tricky. If you're always fighting with your partner, and the peaceful times are a rarity, something is wrong and you should probably consider moving on. But here's where people get tripped up. If you NEVER fight, something is probably wrong as well. Everyone has disagreements about certain things, and the healthy thing is to discuss those differences of opinions. If you are drifting through your relationship, never discussing issues or butting heads at all, then you aren't properly communicating. One or both of you is holding back and not letting their true feelings be known.
If you disagree with something that your partner says or does, tell them. You don't have to yell at them or start a huge fight, but these issues should be discussed. Typically, you can come to a civil, reasonable agreement on the matter. But if you bottle it up inside and never say anything, that will build up into resentment and anger, and eventually it'll all come spilling out.