It happens to everyone at some point or another, but when it becomes habitual, it is a self-defeating nuisance. Negative thinking can steal your energy, motivation, and dreams. It can impact your health giving you muscle pains and headaches. But as someone who has had to seriously work on overcoming negative thinking.
I have to say it can be done easily and quickly. I learned them mostly while raising my own children and was astonished how quickly each trick transformed thoughts, feelings and outcomes.