Nah, I don't hold back. I'd be insulted if I found out my opponents weren't throwing all they had at me, so I don't do any less. If I find myself at the top of the lobby leaderboard more than twice in a row however, I back out of the lobby to find different opponents. I've been in a few lobbies where a player of markedly higher skill was dominating game after game after game and it kinda ruins it for the rest of the lobby, so on the rare occasions when I find myself on a winstreak I don't stick around.