The first thing that I recommend is to get in touch with just how much you are suffering, how many wonderful situations are being ruined by your negative anticipation. Think of your day. Just an ordinary day, and do an honest inventory of how much negative anticipation plays a role. Make up your mind that this is going to change. You are not going to be a prisoner of negativity any longer.
The second thing that I recommend is that you "catch the spook", i.e. become aware of the negative thoughts and images when they start. Listen to them. Maybe write then down or record them. What is the "buggie man" saying too you. What "what if" words and images are you using to frighten yourself?
The third thing you can do to free yourself of the tormentor is to refuse to take the thoughts. The Bible says, "take no thought for the morrow". Argue with yourself, the tormentor, the spook, the "buggie man". You can disagree with the negative images. I recall when my mother or dad would begin to tell me why they did not want me to do something, that it was possibly dangerous or that I could get in trouble, I would argue with them. I would disagree. In the same way you can argue with your negative anticipation.
There is one thing that you can do as a practice that will positively influence your life in every area. When you understand the benefits and methods of meditation and mindfulness, and make it part of your life, you life will radically change for the better. When you learn how to think differently, you life will change. Mindfulness and meditation create serenity and calmness. You can learn how to enter into the "serenity zone" in every situation. You mind can "come home" and become centered and calm. So many believe in medication rather than meditation.
Become a student of cognitive freedom. Learn how to manage your mind through reflection, mindfulness and meditation. Learn how to breath, relax and let go. If you do not know how to do something, you cannot enjoy those benefits. So, make up your mind to give up negative anticipation and begin to live in the zone of peace and calm. Enjoy your days.