If you don't want to spend time learning and practicing fighting techniques, but you're worried about how you'll fare in a fight, add this to the long list of reasons to keep yourself strong and well-conditioned. Technique is a strength multiplier, and you don't have any technique. An experienced fighter is a wonder of efficency and minimal effort; you won't be. It's amazing how fast you can get tired in a situation where you're going all out (and it's a bad idea to work any less hard than the other guy -- that's another strategy that's only for people who practice and have real skill!)