I just had an aram where I got Malphite in champ select. Another player had Nasus and requested a trade. I was feeling nice so I accepted. They instantly rerolled Malphite for Ryze. I asked him why he just rerolled Malphite and he called me an ass. At the same time, another member of the team told me to reroll Nasus because he sucked. I didn't reroll Nasus and dealt with the harassment of Ryze the entire game while we lost. I dealt more damage than Ryze, and I'm pretty sure I died less. Ryze also harassed Leona for engaging the enemy team.
It seems like the games where I play like garbage and get carried are the ones that I win, and the games where I play well are the ones I lose.