Create a default happy thought. That no matter what the negative or bad thought is, you automatically go to your happy thought. You feel the feelings of having that now.
Create this thought right now. Don’t worry about it being perfect, you can change it later if you want. The important thing is you pick a thought right now.
Because when you are feeling down or thinking of something “bad” it is more difficult to come up with something good. But if you have an automatic one you go to, it is easy.