Damian,
Restorations can get the better of the best of us. I usually struggle with time! I just don't get enough of it - too much work, not enough play!
It's s bugger when life gets in the way, but remember you should enjoy it so as Steve says take a break from the panel work for a while. I once spent 3 weeks solid on a rolls Royce silver cloud re spray where I took it to bare metal and had to virtually skim the whole car in filler to get rid of all the imperfections. I got so depressed and my hands were sore and bleeding from the sand paper.
Could I suggest maybe if you are struggling with the filler work, see if you could spend a few hours with a panel beater in a bodyshop and pick up a few tips.
Also the Italian car show is on at Brooklands next Weekend. Come down and we could meet up and discuss tactics!