I really like how Mark Manson took the various repeated ideas around self-help and ranked them from least helpful to most helpful. At the risk of spoiling it a bit, the number one thing you can do is something I've recommended to my team before:
Doing anything when you don't want to do the thing also has robust positive effects. And if you were too intimidated or too scared to do the full thing, breaking it down and only doing part of the thing has highly replicable, repeatable positive effects to the point that it's actually more effective than a number of therapeutic modalities.