It depends on whether it's a situation that matters much or not. I'm generally a big fan of fighting things rather than just accepting crap. There are times, though, when some things aren't worth fighting for; and it can make more sense to just go with "flight" of one sort or another. Then again, what we can discover is that even in times when we don't think something is worth fighting over, we discover that adrenalin and/or instinct kick in - and we find ourselves fighting against our own better judgment.
Having said that, I think it's best to pick one's battles, only fight for what matters, never fight over what doesn't, keep in mind that all fighting doesn't necessarily involved physical fighting (particularly when there's no physical threat), and fight effectively when winning that fight matters.
I think we have both instincts for a reason, which would to me suggest that there are times when either and/or both are required.