The skill of showing up.
Showing up is more than half the work done, maybe even most of the work.
That's what most people fail to do. They wait for permission to show up. They listen to the voice inside their head that persuades them to wait, that tells them that later is better, that safer is better.
So, the people who show up, they get a head start over many who might be more talented or skilled than they are, and rightly so.
If there is one skill that can make everything better, it is to put yourself in places that will take you to where you seek to be. Like Pressfield says in his book by the same name, "Put your ass where your heart wants to be".