The final couple of thoughts/rules - call them what you will!
Firstly, tackle the backolg methodically. You'll need to work out your own method. I have some thoughts, which I might post another time - but I would advocate that you do not start at the top of the pile (physical or electronic) and work your way down.
Secondly, set realistic daily targets and stick to them. making progress against these targets is a great incentive to keep going - especially mid-afternoon on day 3, when you feel thoroughly jaded (the Scots word 'scunnered' covers it very well!).
Finally, take a few moments as you're tackling your mountain to remember something positive from your break ... then start again until you hit your target for the day!