in a matchmaking system like LoL uses you are going to lose half your games. that is a fact.
so the only way to spend more time winning than losing is to surrender. in fact the best way to maximize your fun is to surrender every chance you get.
if you are losing but your team scales well and you feel like you still have a 40% chance to pull out a victory you should surrender. you only get to win half so that loss is coming anyway. if you pull out a victory after losing most of the game it isnt worth it.
every win creates a future loss in matchmaking. by losing most of the game and then winning at the end you have wasted a win on a game that was not much fun most of the way through and caused yourself a future loss which is dropping more fun.
surrender. surrender early and often and at every opportunity and you will have more fun in this game.