Instead of focusing on a goal for three years, try to focus on a goal that you can achieve in two weeks (or whatever your default attention span is)

Design each two week goal so that you get a dopamine rush from doing it, get some value out of it, and it also helps your long term goal.

I share my attempt at doing just that here: https://www.zainrizvi.io/blog/do-more-by-doing-less/