Until my late twenties, I had difficulty with longer projects. Time management was not part of my schooling. If I couldn't finish a paper or a book in a month or two, I did not finish it, period. This shortcoming was something that prevented me from proceeding in school. (And from doing many other things, come to think of it.)
In my late twenties, I decided this had to change. I picked up embroidery and started increasingly demanding projects. This form of tapestry is the most tedious way to create or re-create patterns, slower than drawing or painting.
I learned how to parcel energy for the long haul, how to muscle up for the draining middles of longer projects when the enthusiasm of the beginning has worn off and the tailwinds carrying me to the end were not yet blowing
I took this on as a disciplinary matter, not for its own sake. But the concrete results were there to remind me that YES, I CAN.
My efforts served me well later when doing restoration on antique textiles, and of course, with my writing/revising and such.
So this is where I am today, back to work writing a new story. If you're working on your taxes, that'll be over soon, and then comes tomorrow. On this final stretch, grab hold of the saddle and don't let go.