Like sports, instruments, and any other developed skill, there will be days you feel like it and days you don't. The key IMO is to pace yourself: don't overwork on days you feel like it, and force yourself to work -- even if just a little bit -- on days you don't.
For software, having your code in a public repository like GitHub provides some socially-based motivation to keep your projects active. Just the simple act of regularly committing small changes can provide you with a sense of momentum -- and bonus points for raising (and fixing) issues, etc.
For days that you aren't on your A-game, it's also helpful to have made a TODO list from a day when you were thinking more clearly, so you can work on a relatively simple task just to maintain momentum.
Another key is to have a "big picture" goal that your projects are helping you towards. There's no reason you can't start now putting together the basic structural code (say, some core machine learning algorithms) for a later startup -- or even try your hand at writing an end-to-end web app and hosting it for free on Amazon. Whatever your end goals are, you'll be more motivated if you are writing code that helps you get there, not just code for learning's sake.
For software, having your code in a public repository like GitHub provides some socially-based motivation to keep your projects active. Just the simple act of regularly committing small changes can provide you with a sense of momentum -- and bonus points for raising (and fixing) issues, etc.
For days that you aren't on your A-game, it's also helpful to have made a TODO list from a day when you were thinking more clearly, so you can work on a relatively simple task just to maintain momentum.
Another key is to have a "big picture" goal that your projects are helping you towards. There's no reason you can't start now putting together the basic structural code (say, some core machine learning algorithms) for a later startup -- or even try your hand at writing an end-to-end web app and hosting it for free on Amazon. Whatever your end goals are, you'll be more motivated if you are writing code that helps you get there, not just code for learning's sake.