I had to do this in my life.
The projects I want to do can take hours of concentration.
But reality gives me 5-15 minute increments throughout the day (except night, which is why I’m up right now).
So I learned to have logical stopping points with ANYTHING I do that’s at about the 15m mark. I can usually stall an extra 10m, cut off, and move on to whatever chaotic thing is SOO DARN IMPORTANT that have to packup and leave for hours about.
If it’s a super quick thing, I can do it right away and return to my task but usually that’s followed by another interruption within 10 minutes, so sometimes even that 15m logical stopping point stutters along for hours