I,too, use the reward system. I will tell myself "just one more block, or one more seam, & you can quit." It's like the children's story: "Inch by inch, life is a cinch; mile by mile ....(something negative that I can't remember)".
Anyway, get it done & the degree of relief you feel at the end should be invested whenever some asks you to do " a little something." Shout "No! I'm backed up & can't possibly take on another project right now!" Then smile, and walk away.
Best of wishes!