In business, I make it a habit of dealing with the most annoying, or unpleasant, or tedious tasks of the day first thing in the morning so that I can deal with them, move on and enjoy the rest of the day, with those things out of my hair.

With music it is the same. I tackle the most tasking, difficult tunes first and give them all the time they require, and then reward myself with something simplistic but fun to play. With recording, I do the "grunt" work portions first so its out of the way and save the parts I really enjoy playing for the final parts of the recording.

I find that for me, dealing immediately with the things that irk or annoy me (whether music or otherwise), and then moving on gives me more positive energy for other tasks. I think procrastination of anything if left unchecked becomes misdirected negative energy, which can snowball (into other areas) and affect a person's general well being.