The go-to book for this problem is "The Worry Cure" by Robert Leahy. The book starts out by explaining why many popular methods for fighting worry are actually ineffective or counterproductive - for example, trying to assure yourself that the thing you worry about will most likely not happen. There's a better way, and it is explained through a series of simple exercises in the style of CBT (cognitive behaviour therapy).

I first read it ten years ago, and I still use the tools on a weekly basis. Changed my life, and the lifes of two other people I gifted the book to.

You can get a gist of his method in this podcast: https://www.listennotes.com/da/podcasts/the-aict-cognitive/d...