Its a common filmmaking/boorwriting technique. The hero starts by losing the fight, then he goes away to train more / realize his true power or all that hoo-ha, and then come back to kick the baddie's ass. It is used because it builds suspense. Suspense keeps readers interested and attentive.

Yeah, that's a tried and tested formula for getting the audience to relate to the hero. Create sympathy, play on the audience's love of rooting for the underdog (our hero), share in the hero's struggle against the odds and glory in his ultimate victory! Feelgood stuff! A typical storyline goes like this; 1.) Meet the hero - he's a nice guy but he's not perfect. 2.) The hero has the same problems as you. He's had a bad experience that haunts him, he's misunderstood and he does not have good luck with women. 3.) The bad guy is not the type of person YOU would like. In fact, he's the kind of guy you would like to take a baseball bat to if you could get away with it. 4.)The hero was minding his own business/ trying to do good but got his ass kicked by a bad guy who laughs at him. 5.) The hero is filled with righteous indignation. He overcomes this defeat and becomes stronger person in the process. 6.) The hero vanquishes his foes and rises victorious - up where he belongs - he get's the beautiful girl - and he will never have another problem again for as long as he lives. He receives due public acclaim for single-handedly saving the whole goddamn world. Variation (optional): 7.) Sometimes the hero dies. After much grief it is happily realised that somehow the hero will live forever... because his legend will continue to inspire generations to come/ he has left behind a son/ he has become a benevolent ghost! ☺