One option: try this Serenity spread:
http://www.tarotforum.net/showthread.php?t=92235 Or there are others about letting go of things in the Spreads section of the forum.
I do get like this once in a while still. What I personally do:
A) recognize there's one problem here that I can actually fix, and that's me being obsessive on a given subject--sometimes, that alone is enough to stop the process, but if not, then...
B) do ONE one card advice reading: "What's the next thing I should do on this subject?"
C) stop reading on that subject until I've actually followed through on that advice and given a bit of time for things to happen as a result of that advice
D) repeat steps B & C until either something changes or I reach acceptance with the fact that the situation cannot be fixed--usually, it's the latter
What I don't do: ever read on that subject again about anything other than advice. I never draw more than one card, period; this includes more clarifiers--if you don't understand the advice, think on it a while or ask here, but drawing additional cards only feeds your obsession.
And I never do another reading on the subject until I've followed the advice from the previous reading (and given time for that to work!) Often, Tarot makes it quickly obvious that the situation is going nowhere, like it or not. (My favorites I've gotten: my Significator, to say "what you already are is enough"; 8/Swords=accept your limitations or those of the situation in order to free yourself; 9/Swords=most of the problem at this point is your reaction to the situation; 10/Swords=it's done, it's over, it's well beyond fixing, give up already, get out of your own head and go do something else, for pity's sake!)
The more I've done this, the less often I've had to do it, because let's face it, being told over and over in different ways that there's nothing you can do to change the problem gets rather boring. And even though on a strictly logical level, I already know it can't be fixed, being told by the cards that there's nothing I can do reinforces that enough to make it easier to live with.
Sometimes, I'll get actual, useful advice to follow, like a getting a 2/Cups and recognizing that I need to act with loving-kindness towards those involved, for example. Or a court card that indicates who I need to approach or what traits I myself need to practice to bring things back on track. This advice may not totally resolve the problem; at times, it's one of several things you need to do. Often it's just another step on the path to acceptance. But it has happened where I've followed advice from a single card and watched a particularly thorny problem simply vanish.
Honestly though, I think it's best to just force yourself to stop and put the cards away as soon as you realize you've fallen into that cycle. It's rarely productive to spend time trying to fix these things; 90% of the time, there's nothing you can do but accept things as they are and either walk away or find a workaround that allows you to function well in spite of the problem.
