This divide and conquer thingy sounds like it makes a lot of sense. I've decided to cut down a bit on the drum and bass, and focus on trumpet right now. Because of the embouchure this is quite difficult to combine with flute, but I'm managing. This doesn't mean I'm not playing any drum and bass anymore, but it's just not a priority. I've got some experience with learning how to play instruments, so I know I'm not going to become a great drummer in a month. Also not in a year, or two years. I'll probably never become a really good drummer, but that's all relative. Like DusK said, becoming mediocre at everything sounds like a great bet, since it'll be useful for my own recordings and compositions. The same with bass, trumpet and whatever other instruments I might wanna play later. And I just generally always want to keep improving, no matter how good, mediocre or bad I'm at it. I think that kind of mindset is important if I want to make a living out of music.
After downloading the app Garpocalyps recommended to me I've been getting my music making a bit less chaotic and more streamlined. I'm starting really easy, with just practicing bass once a week, drums once a week, trumpet daily, composing daily and flute whenever I've got some time left. But I'm planning on getting things a bit more frequent.
Carbunkl sums it up pretty well.
Everyone, thanks for all the advice!! I'm gonna keep all the words that have been said here in mind.