Forcing yourself to code

How do you do it, guys?
I seem to only really code when I really feel like it.

tl;dr how can I improve my coding stamina?

I try to do so too. It's hard to pick up an arbitrary project. Most of the ones that do succeed come from "holy shit dwarf fortress is too complicated, I'm going to streamline it and reimplement in in Common Lisp".

5 weeks later, I have the hand-crafted libraries but no game :(