I wish I could tell if I'm the trash player that keeps dragging everyone down or if I just get matched with terrible teams. I am absolutely terrified of playing Comp (or even Quickplay, really) because I usually blame myself for losing and don't want to pass that on to the other 5 hapless players who are burdened with me.
(granted, this comes off of a loss with a Reaper on our team that wouldn't target tanks and then, at the end, claimed "you guys take this game too seriously" when called out on it, so that example probably wasn't me)