I never want mine to, and it always does. Especially when there's something negative to think about, it can never just sit there and think happy thoughts...not as obsessively as bad ones, at least. Seriously, at the end of every day or if I'm just sitting there with nothing else to divide my attention, I sit there and pick apart every little tiny detail I might have done wrong or not as I would have liked to have done, I analyze everything, hate myself for it, and then move on to shit that's going on that I worry about, and as an added bonus, those are almost always things I can do absolutely nothing about at that moment. One of the big reasons I listen to music so much is because it gives me something to focus on other than all that,
This.
Another big one for me is "Man, I need to start working out more." and I'll go over how I'm a failure for not being consistant with working out. And I only ever think about it when I'm laying down to go to bed. I never just think, "Hey, I should go work out." in the middle of the day when I have nothing to do.
