As somebody who has suffered basically the exact same thing, one book that has immensely helped is: https://www.amazon.com/Self-Directed-Behavior-Self-Modificat...

Essentially I found that I could tackle any task, but on the first flash of some other more exciting idea, feeling or sensation, I would drift off.

The book boils doing to finding your own Antecedents that Lead to Particular Behaviors that you want to change.