Once acquired, the habit of worrying seems hard to stop. We're raised to worry and aren't considered "grown up" until we perfect the art. Teenagers are told: "you'd better start worrying about your future". If your worries aren't at least as frequent as your bowel movements, you're seen as irresponsible, childish, aimless. That's a "responsible adult" game rule.
Strange as it may seem, you want what you worry about. Or at least that's what you inadvertently tell your brain when you worry. On one level, your brain can't process "negatives". If you tell it: "don't think about crashing the car", it can't help being "attracted" to the thought/image of crashing.Consciously, worrying is about preventing/resisting/avoiding X. Subconsciously, it's a reinforcement of wanting X (at least to the extent of wanting the experience of X in your mind). Consciously, you're pressing on the brake; subconsciously you're pressing on the accelerator.
The difficulty is that your "feet" (to continue with the analogy) are tied together. So, to stop accelerating, you must also lift your foot from the brake. But you refuse to do this (which might be sensible in a car; but your brain isn't a car).
You somehow have to persuade (or con) your brain into thinking it's safe to lift both feet from the worry pedals. For serious anxiety disorders, phobias, etc, many people go into therapy. The end result, if successful, is equivalent to learning to lift both feet (ie to "let go" of the worry/fear).
For relatively "minor" worry problems, you can use psychological gimmicks to "con" your brain into letting go of the worry – eg the worry postponement and "focused punishment" techniques described above (both have the effect of getting you to "lift both feet" from the accelerator-brake).
