Anxiety Support Group
Anxiety is a physical condition marked by intense and persistent feelings of distress, fear, angst or dread. General anxiety caused by routine day-to-day stresses usually passes quickly and is experienced by almost everyone at one time or another. However, such feelings that linger over time and are very difficult to cope with, and which lack a clear cause, may indicate...

So this makes it harder but even more necessary to retrain your brain to only think positive thoughts as much as possible.
-let them come and go like the ocean lapping on the sand
-keep thinking them until your mind tires of them and you find them funny
-do something to take your mind of it, like a hobby, listen to music and sing along, exercise, read a book
Hope that helps.