The piece I’m writing surprises me because I want to develop it quickly yet hours of practising are required in order to get it to a place where I can reliably execute it. Delays my quick writing fantasies, can’t write the next parts until I know the first parts, only then can I relax and imagine where I might go next. The last melodic piano piece like this happened over months. Didn’t Bach write a bajillion pieces with 30 screaming children were hanging off of his shoulders? Wonder if people like him performed everything they wrote or if they also wrote (notated pieces) whether or not they could perform it.