There was one time where I skyrocketed up the ladder because of ten wins in a row. Then the next day I was back down because I lost five times in a row.
In other words, there seem to be days where everything goes right, and then there's days where nothing goes the way you want. I just don't play if it's one of the latter days. I think it's all in your head though. Like what Wolf said, it's all about team matchups and your team could be the best team in the world and it still won't win 100% of the time. The trick is to stay positive and level headed no matter how well or poorly you're doing. If you can do that, I don't those days would really exist.