When it happends I just try to take that feeling as it is and walk through it, if you know what I mean. In my case, I know that there usually is a reason for me feeling that way, when I'm feeling that way. I try to find out what might be troubling me, and if I find the reason, well, the bad feeling just kinda recedes and becomes manageable. If I for some reason can't find a reason, for instance, because I'm too troubled to think clearly, I just ride it through. I guess that, at that point, I tell my self that there is no point in bothering one self too much with things that doesn't make any sense.
I don't know if I made any sense right now, but, well, there you have it, my way of dealing with it.