The trick to feeling ready BEFORE you start is "state management."
That feeling of 'ready' is normally a reward for accomplishment, and it tends to lead to more action. But you can hack this resourcefulness before the work even begins.
The people who seem naturally disciplined aren't wired differently. They've learned to manufacture the state that makes action feel natural. Just like any other skill, it can be learned, practiced, and eventually automated.
What state of mind would be the most helpful for you today??