Heh... here I thought I was unique
.... I found that constant random thoughts going through my mind was making me a sour person to be around as well. One of the things I found helped, and it was kind of inadvertent, was a prescription. My doctor put me on Lexapro to help elevate my mood. After taking it for a few weeks, I found I could focus more centrally on one or two things, instead of constantly running things through my head, I noticed I was more relaxed as well. I know you mentioned you don't want to be on pills, but this was what helped me out, and I wasn't expecting it. I found I could also resolve issues more easily, and actually not care about trivial things, just as roboshark mentioned. Whether you want to take medication or not is up to you, but it may be worth looking in to. Hope that helps you some