One possible heuristic is: input task into LLM, let it do the work, and make sure you understand everything it spits back out. One potential drawback is there is some value in having to figure out things yourself. When learning a language like French, you wouldn't get very good at speaking/writing if you told the LLM "write this paragraph for me in French", and went and verified if it was correct. At the same time, it massively accelerates getting things done. You kind of need to fail and have something correct you.
On the other side, something like Advent of Code which is purely self-motivated and for fun, you can write everything yourself, but at the same time, you could just input it into the LLM and get rid of the tedium of typing things out you know will work, especially for the first 10 or so days. This is a fast feedback loop on the "meat" which is "do I know how to solve this problem?".
I'm having a hard time figuring out when to reach for LLMs and when not to.
Hopefully someone who has more understanding of educational pedagogy can chime in :)