Everyone needs to choose their battles wisely.
I am not saying you should turn away from a strong enemy, or that cowardice is the right route. Instead, what I am saying is that you need to insure that you know your enemy.
If you are going to engage a target, then make sure it is the right one. Do not overestimate your enemy, and end up aiming six feet over their head. Do not target a perceived enemy for the flaws of another. Do not paint an unrealistic image of your foe, because that will make it harder to gain allies. If you are going to fight a battle, make sure to do it on realistic grounds. We cannot defeat a foe by punching at shadows. We cannot garner allies through spreading lies, to do so is dishonorable. We should make sure our allies know what is real as well.