I have hundreds of eight bar loops. For years I read that as a discipline problem, and every bit of advice out there agreed. Sit down, push through, finish what you start.
It isn’t a discipline problem. Starting is a different skill from finishing and being good at one tells you nothing about the other. The loop is the part I’m good at. The part where a loop becomes three and a half minutes with a reason to keep listening is a separate thing I’d never actually practised.
So I practise it on its own now. One session a week is finishing only. No new ideas, no new sounds, just taking something that already exists and deciding what happens at ninety seconds.
The output is worse than the ideas were. A finished track from that session is usually less exciting than the loop it came from, because the loop never had to be anything but a good eight bars. It gets easier. It also gets released, which the loops never did.