A meditation: sit somewhere comfortable, work with your hands, and think of nothing.
How to think of nothing: That's just a figure of speech because I don't think anyone is capable of sustained nothing-thinking, but you can stop a thought from taking over. As a thought goes through your mind, do not let it amplify and lead to more thoughts. You're in control. Say: Stop. This makes you aware before the thought carries you away to the next thought and the next and the next. As with all worthwhile things, practice makes perfect or near-perfect. Give your mind a rest, especially from negative thoughts.