Sometimes you win, sometimes you LEARN.

At the end of the day League is a strategy based team game. If you lose the other team was simply OVERALL more skilled. You can take away many things from a loss. If you briefly review each game you lose, you can glean much experience to improve your game-play AND how well you interacted with your team. Aside the occasional anomaly (Griefing/DC) every ranked match is roughly even.

When you lose, take advantage of that opportunity to LEARN from your mistakes. Even the best players didn't get to where they are by winning every game. Just remember win or lose, the important thing is to HAVE FUN and make sure others are HAVING FUN.