I think it's just a case of the tunnel being so long I can't see any light at the end with the added pressure of work being so hard ATM. I won't give up yet.
sounds like you need xenon lights

if it is a case of needing to do a lot to it like you say, you can still make it happen slowly.
make up a list of things that need doing, but do it in what you would estimate to take about 1.5-2 hours for each section of the larger job, then, scedule time in your week that allows you do get that small part done.
it seems hard to do i know, but people scedule in time during the week to go to the gym, or watch thier favorite shows, ect ect.
you may need to make that time in the evening, after dinner and a bit of a sit down and relax.
i am doing a similar thing, i try to get at least an hour in the shed at night, 2 nights a week, i know its not much, but it does make you feel like you are actually doing something,
tell your partner, its personal stress releif time.