Habits Beat Motivation
We've all gotten really excited about a new project; building something interesting, learning something new. Things go great until they don't. You get stuck in gumption traps, you get short on time, and the honeymoon phase of the project wears out.
Motivation alone isn't enough to get through non-trivial things. You need to set good habits. Habits externalize your accountability for things that are important to you.
Rather than hoping that you'll be motivated every day to work on learning that new language, just know that at 9:30, every day you put half an hour of work into it. Then there's no decision to be made or motivation to muster up. Put it on your calendar, if you must!
You're not always going to be motivated and that's ok, but you can set good habits to keep you going when motivation wavers.