It's not about finding someone who won't fight with you or make you sad. It is about finding the person who will be standing there wiping the tears away, holding you in their arms after a fight. The one who will never leave, no matter how hard it gets.
It's harder than it seems to turn and walk away. But it's a thousand times harder to turn away with a smile and a whisper of "I'll be fine. Don't you worry." When all you want to do is curl up, hold yourself and cry your eyes out.