Howdy,
Reiden had some good advice. I do the same thing with stuff: super motivated, crash and ignore, super motivated, crash and ignore…
I found I had to take the time when I was motivated and carefully make sure to NOT do as much as I wanted to. Make the amount you allow yourself very small (like a treat) and don’t let yourself do more until the next day. I found that, while frustrating, it keeps my interest much longer.
It might not work for everyone, so you’ll have to decide whether you can use it or not.
Z-man