I'm sorry to break the bubble here. Any one who has seriously pursued boxing or been a part would disagree with most answers given here.
The most common one being: "Defeat is not declared when you fall, but when you fail to get up". It might be true for life, but not for boxing. If you fall down 3 times in a round, you lose by TKO. There might be slight difference in the number depending on the governing body, but mostly it is 3 or 4.
Do not step into the ring on the sole belief that you will win because you want it more than the other guy. That doesn't happen in life, that doesn't happen in boxing. You will get pounded to the floor if you aren't prepared. I've been there. Believe me.
Everyone has a plan until they get punched in the mouth. The winners are those crazies who stick to it against overwhelming odds or the ones that are smart enough to come up with a new one. To win you must either be crazy or smart or maybe both.
The only thing that could be surely said about boxing and life is the unpredictability of both. One moment you have the upper hand, a small mistake and you are on the ropes, defending to just stay standing. When you are getting the shit beat out of you, an opening will present itself, take it and you turn the game around.
And remember, nothing hits as hard as life, unless it's that guy from my gym who looks like a tank but moves like a race car. My jaw still hurts!