The War of Art, by Steven Pressfield. It's short but sweet. It's a writers description of "the resistance", an invisible, ever present force that actively works against you when you're trying to ship. More generally, it works against you when you "[try to do] any act that rejects immediate gratification in favor of log-term growth, health, or integrity."
The first part is titled "Resistance: Defining the Enemy" and is a great description of what the resistance is and the ways in which it works to defeat you.
The second part is about how to conquer the resistance by "going pro". There's a lot of pieces to this, but basically, it means figuring out how to show up every day and doing the work, day in and day out, with the explicit goal of conquering the resistance.
The third part is a higher level discussion of the resistance, and at least to me, was not as relevant.
Highly recommended book if you struggle with the resistance when trying to ship.