Try something new everyday. A new food, a new nail color, a new route home from work, a new brand of shampoo. Try it for a month with the goal of finding at least 4 things that weren't in your life when he was in it.

This is a life adaption of cbt. Instead of just changing your behavior, change (with good new things) the pattern of your life. It doesn't have to be drastic, it just needs to be new to you. Focus on the person you are and want to be. Find what brings you joy and let go of things that don't. Even if it's temporary.