Most people think this aphorism means you should drop some of your upcoming battles to win some for which you care more.
From our perspective, however, it means something completely different. What that means to us is that we should push on with all of our battles, and then choose the ones in which we are losing and focus on turning them into wins with vigor. Our energies are guided by principle, so conceding a battle means compromising on principles, which we do not believe is the correct approach.
More importantly than picking battles is understanding that you will lose many, and that that's okay. The important thing to remember is not how many times you win, but rather how you work to make those wins possible.
How about you? Do you work by principle?