Why is this so?
For the most people, it's because either they haven't formulated their mission strongly enough or they get distracted from their mission to do things that don't matter.
There is one medicine which works wonders (at least in my case). That's a deadline. Make sure you give yourself external or internal deadlines to hold yourself accountable.
For example, if you want to learn to play hymns on the organ, set up a date when you can play and sing hymns together with your friends or family. If you play at church, it could be as simple as preparing a certain number of hymns in a certain way for your next service.
What happens, if you fail to learn those hymns on time? You may disappoint your friends or family or your congregation with your boss, or your may fear that you won't reach your potential.
When the idea of not reaching your potential becomes more difficult to bear than the idea of sitting down on the bench and practicing the right things the right way, you will find the motivation to spend the time necessary to master the art of hymn playing.
Next: Read this before your next practice
Duo VII Ave maris stella (in Versets of 2, 3 and 4 voices, Fabordones, Intermedios, p. 8) by Antonio de Cabezón (1510-1566), a blind Spanish Renaissance composer and organist.
A Great and Mighty Wonder