Motivation helps. You need some gig to be aiming at, or a teacher to impress, or some other reason to put in all the effort it's going to take.

One point that has not been emphasised is to isolate the difficult bits and work at them till you can handle them at the same speed as the rest. If you don't like metronomes, at least record yourself and play back the results. One sign of weakness can be a tendency to speed up and actually rush the difficult bits, and without metronome/recorder, this can pass unnoticed by the player.

But don't forget different people have different levels of motor co-ordination, so some will always have an instrinsic advantage over others. That's my excuse, anyway.

Oh, and welcome, Cantrip. You've found a good thread to start in. (But the ones that end with blood on the carpet can be fun too!)