A list of goals. I work as an intern games developer, while not working i also do online study courses to help improve my coding or analytical skills, developing my own game and playing games. There is one thing that boils my blood, it is waking up without any clear idea of what i should be looking to achieve for the day. Managing your time effectively can be a pain in the arse especially if your days are mainly consumed by working and travelling but if done correctly you should have enough time to work, enough time to play and enough time to code your own game, while also feeling accomplished and sleeping easy.

But be weary of overshooting. Don't make your list of goals incredibly vague that it still leaves you wondering about where you should start or when to finish. Also try to estimate the time needed to accomplish a given task and look to put a cap on the time spent as something. 

I also find that looking for inspiration through music or reading helps a lot.