Where did the fun go?

I've been playing League for 2 years now and I've found that my level of enjoyment has decreased as my summoner lvl increases. Am I expecting more from myself and being more disappointed when I have bad games or have I simply hit my skill peak and should accept that.

Before when I lost a game I thought "Oh well on to the next one" now its "Wtf did I do wrong, who's fault was it" and I spend and hour later contemplating on how the game could have been better or how whoever stomped my ass was using an OP champion.

What has happened to me? I used to enjoy the game. I've tried taking breaks from it. Messing around trying odd champions in odd roles. Maybe trying ranked screwed me over and now I take things too seriously.

Please some help or advice would be much appreciated I'm sure others are in the same position with this game