The act of doing things. Sounds simple at first glance but of course it depends on the task.
It's actually one of the best countermeasures to stress in my opinion.
It's easy to plan too much, yet only action gives experience. Planning fallacy.
Here is a paradox: Motivation drives action but action also drives motivation: So you need something else to drive you to start the loop first. This may be the case of why it's hard to start action at first. However, bad results may also drain motivation to action, so you may need to detach from the outcome.