Obligatory: Don't learn programming languages. Learn programming problems and which languages were developed to solve these problems.
Also, you say you've reached a reasonable level of fluency with javascript and python. What does that mean? Having a grip on the syntax is different than being comfortable with half a dozen libraries and building an application that solves real user problems.
If you're learning for the joy of learning that's great! But maybe then try something completely different than the C family of languages. Try Prolog or Assembly and try to make some applications!
Want and grit. At some point you'll have to grit it out. You have to make it clear to your brain that you want it. Make it personal. Want it not the way you want to have a cookie after dinner, want it the way you want to breathe. Don't even want the project, but want to prove to your brain that you are a rare capable human, able to start and finish a creative endeavour independently.
Make work time scarce and urgent. Having a child has done wonders for my creative output. I used to splurge 6 hour sessions kinda working on something..now I get maybe 40 minutes a day. An hour if I'm creative about it. But heck, does that hour get applied like nobody's business.
Hope this helps, best of luck!