Sit on a mountain and contemplate your navel or sit on the couch and contemplate your old lava light from the 60s. Just do whatever works for you to still you mind and purge mental clutter. Sometimes just taking a leisurely walk is great for clearing your mind. Walking helps you keep in shape mentally and physically. Reduce mental clutter by not worrying so much.
Negative thoughts are like snowflakes.
They are easy to melt when they first begin to appear and difficult to deal with when they become avalanches. Eliminate this useless mental clutter in the snowflake stage. Remember, one definition of worry is thinking about what you do not want to happen . When you find yourself doing this, reverse your thinking and think about what you do want to happen. You can never finish something that you don't start.