I try to force myself to do 10-15 mins and usually by that time I'm focused enough on something that it's not very hard to keep going. I also try to fix things whenever I find them instead of leaving them for later because I'm much less likely to pick the project back up if I know the work is going to be frustrating.

Every night I make several hours of progress on something. I usually have several candidate tasks selected and that lets me stay productive even if one resists me that evening because I can swap for energy or flow. Just do this every day and things get finished.