Carry games and also lose them

So every once in a while I play Yi. Sometimes I land everything on point and hit the right targets, press q to dodge skillshots, get 3 honors in a game and am even told by someone named draven -insert other part for no name and shame or whatever- that I'm one of the good yis. But there are those yi games that I just get rekt in so hard, and am told never to play yi again. I feel like I'm the same person, but my skill level tends to vary based on the day? Granted yi is probably too strong right now, but it's weird to be complimented for my gameplay and the next time I play be insulted because of it.

Kinda wondering if it's just like a mental thing?