Like many have mentioned, I could have written your post! I am a constant worrier and have very strong obsessive thought cycles (OCD kicking in). One of my biggest struggles is staying in the present moment. It takes great effort for me to do so...here are just couple of things that help me:
Relaxation and Meditation can definitely help - or just a simple repetitive phrase to clear your mind (in meditation they call it a "mantram"). When you find yourself worrying unneccesarily or unable to get a thought out of your head, try repeating whatever calming phrase suits you (it can be one word, like "peace", "calm", etc. or a phrase like "Lord give me strength" - whatever works for you). I have to do this a LOT because I have difficulty pulling the plug on whatever is running obsessively through my brain! Keep repeating it until your mind stops thinking about whatever you were worrying over.
I also try to put things in perspective. When I begin to obsess over something relatively inconsequential like my looks, my house, or what other people think about this, that or the other...I stop and remind myself of all my blessings. I think of women in other cultures or enviroments who don't have enough food to eat or freedoms to enjoy, friends who are struggling with a terminal illness, etc. - not to sound morbid or depressing, but I can more easily appreciate my own situation when I open myself up to the "real" hardships out there.
I always have to remember, "Today!", "Today!", "Today!", even literally saying it to myself sometimes...I tend to live in yesterday or tomorrow :)
Anyway, I am right there with you and it's hard work to stay in the present - but I am much happier when I do!
Panic Attacks (since age 10) & General Anxiety with a little OCD thrown in there
Biggest Challenge - Panic; Biggest Joy - my 3 cute kiddos (ages 1, 2 & 5)