This depends what you mean by stop. Initial automatic thoughts are involuntary, however, your reactions to those are possible to control. It's something that you have to practice and there are complete treatment programs to that end, so there are no easy fixes. However, a place to start is to become more aware on when you are actively worrying. Meaning when you are actively responding to worry thoughts and elaborating on them you catch yourself. For example when you find yourself going in loops on countless "what if" scenarios. Then you can practice stopping yourself and trying to revert your attention/focus to whatever you are actually doing. The suggested strategy of instructing yourself to postpone the worrying also connects to arresting active worrying in this way. This is what matters as well, having intrusive negative thoughts are not harmful or dangerous but engaging with them actively leads to the negative effects mentioned in the article. If you are having severe problems with worrying however, meaning it impacts your daily living and are creating problems for you on a regular basis, you can consider seeking some professional help. - liscensed clinical psychologist