Why am I playing so bad tonight?

I know that you won't care at all about me and how I play but..sometimes It feels so ugly. On my 2 last matches I was playing my favorite champion: Katarina. Usually do well with her but...I failed my lane so hard....now I just feel like shit. I can't play my main champ anymore? ok sometimes it was my computer fault because it turned off randomly (I think it was because the temperature was too high, it doesn't happen often..) well the point is, how are you gonna pass trough these phases where you feel like you're not good and tilting and not having fun anymore..?

(sorry for my bad English I am italian, I am writing this here because on the italian forum they would propbably judge me cuz of my elo and sayin stuff like "learn to play l0l" soooo I am writing this here also because I spend most of the time here.)