As a professional, it's my responsibility to invest in my craft. But I also enjoy taking lessons not related to my field, like The Marketing Seminar from Seth Godin.
You'll find some notes of the courses I took, and if it sparks your interest, you might want to give them a try. But I suggest you do some research before and prepare yourself. The real difficulty is finishing a course and leveraging what you learn to benefit your life.
Testing JavaScript is an online course by Kent C. Dodds to learn how to efficiently test a JavaScript application using the Testing Trophy method. The course requires some experience developing web applications with JavaScript, but it's beginner-friendly on the testing part.
Kwik Reading is an online course by Jim Kwik to help people read faster. Most people learn to read when they're young. Then it's considered done, and that's the mistake.
Epic React is an online course by Kent C. Dodds to learn everything you need to know to develop a professional application using React. It's an intermediate/advanced course that requires some experience developing web applications.
CSS for JavaScript Developers in an online course about CSS from Josh Comeau specifically aimed at JS Developers. It's a one-time purchase with unlimited access to the lessons. The promise is simple: CSS can be fun.
The Marketing Seminar is a 150-day workshop by Seth Godin. It's a more active way to consume his bestseller book: This is Marketing. I had a great time going through the course. Doing marketing the way taught in this seminar is gratifying. You don't have to go against your principles or values.