Obvious advice, on the face of it, but one people mostly ignore.
If you're having an argument, conflict, serious disagreement, whatever - what are you trying to get out of it?
"What's my objective? What's most likely to get me it?"
Or, more succinctly, "What is winning?"
On a related note, you also probably shouldn't fight with people over situations that will straighten themselves out.
Take traveling. It's stressful at times, especially if you're not veteran at it. You should never, ever fight with someone over the next place you're staying/not staying/etc. It'll sort itself out. Worst-case scenario is overpaying for a room or half-sleeping at a train station or 24 hours-open place.
Okay, be careful if you're going somewhere remote and extreme and dangerous. But any remotely developed country? You'll be fine. Things where "you'll be fine" regardless of what happens next usually aren't worth fighting over. And it's never worth fighting if there's nothing to be gained.