5-10 buy in downswing is possible, but be sure that it is a downswing rather than playing badly. If you are a solid winning player I wouldnt worry too much about it, but if you're down 10 buy ins you need to move down a limit and rebuild your roll. Its nothing to be ashamed of, I think many winning players have moved down one or two limits a couple times when running bad.

Just keep playing winning poker and ride the wave.