It's habit. If you can see the good side, make yourself stay there. Yes, bad things do/can happen but they cannot be predicted and they don't happen "more" than good ones. Stay out of the future, stay in the moment. If you find yourself straying into the future; use your good thinking and imagination (takes a good imagination to worry effectively :-) If it is future and no one can know what will happen there, you can make up good scenarios just as easily as bad ones! Make yourself laugh with your good scenarios. When you emigrate, the new location will be much cheaper and you'll live like a queen. In my case, my last move (2005) we sold our old house for $100,000 more than our new house (on the water, I have a horrible view from my bedroom balcony ;-) cost so got a "free" $100,000!

When you worry about brain tumors, remind yourself it's just a headache, take an aspirin and call yourself in the morning, see if it is still there :-) If it is and you get headaches often, then call the doctor and get a workup. Be proactive and "do" something about what you are thinking, instead of just worrying. I go to the doctor every 3 months and just don't worry anymore about many medical things because I know my physical self a lot better than I use to.

Educate yourself about things you worry about. I had a medical emergency in 2003 that lasted 5-6 months and could have killed me 2-3 times; I no longer take my health or knowledge about my body for granted. Part of the problem back then was I had never had a doctor, so no one, including myself, knew anything about my physical state since I'd never been ill before. First thing I did when I moved was get my husband and myself a doctor; now I have over 7 years really good experience and knowledge about myself and my health issues.