Assuming you're playing even games (P(win)=.5), losing streaks of up to 6 games are to be expected from time to time. If you lose more than that, that's when you're probably in a rut. Mistakes that cost you games are probably one or more of the following:
1) life/death misread - the only way to remedy that is to practice regularly
2) saving a group at all costs when abandoning it would be more sensible (stingy)
3) trying to kill an opponent's group at all cost (greedy)
4) invading too deeply instead of reducing (greedy)
5) reacting to all of your opponent's moves instead of evaluating on your own whether they're sente (submissive, not trusting your reading)
6) ignoring your opponent's sente (stubborn or misreading)
Any form of single-mindedness, really, because you lose sight of the big picture.
It's not easy to fight the feeling that you're giving too much to your opponent "if I don't cut here", "if I don't invade there right now!" or "if I don't save my / kill his group"... but I think you can refocus by
counting. It gives your agitated, perhaps restless mind something useful to do, if you make it a habit you will get tremendously faster and better at it... and it enables you to choose more sensible strategies. "Am I still okay if I abandon this heavy group and take points over there?" "I am ahead by about 10 points, seems I don't have to start a do-or-die invasion anywhere..."
If you don't know where to play, and have a lot of time on your hands, you can also replay the game rotated by 180 degrees to get a "different perspective".
