The worst losing streaks are those that you are sooooo close to winning, then you do something horrendously stupid and lose the game.
But try to just ignore it. My rating goes up 200 one day and then down 200 the next day. Just accept the fact that you will always have good/bad games.
A lot of players get frustrated because they think of the hot streaks as their "real ability" and the slumps as some abberation where there must be something unusual happening.
Talk about hitting the nail on the head, kinda funny to realize how true this statement is.
Maybe you're just not as good as you think you are. And maybe you're not even as good as you are. No offense, but I think we all need to reassess our chesss from time to time. I get down over losses sometimes, and I always come back to the question of how do I get better? Some say that playing the game itself will only improve your game by so much, and that you will hit a plateau. I would suggest that you stop playing against people for a week or two. Go over your losses, and see if there is anything common among them that you may be able to correct. Something as simple as immediately addressing potential threats instead of ignoring them while focusing on the offensive. I also like to come back to "Bobby Fisher Teaches Chess" and just enjoy some of the "fun" combinations therein. That's my 2 cents. Hope it helps.
My other gaming passion is Go. So whenever I'm burnt out or in a slump with chess, I take a break and play some Go instead (if I'm feeling the need to game at all). Sometimes a break is necessary to refresh the mind, however you choose to do it.