I practice mindfulness. It's as easy as it you are cutting veggies for a salad be 100℅ effort on doing that activity..focus on the colors, the contours,what the veggies feel like in your hands, etc. It's important to note that your head will naturally to back to the negative stuff. When that happens gently bring yourself back to the salad without getting upset or judging yourself in any way.

A lot of people use focusing on their breathing since that is always available. The more you practice this the easier it becomes.