I agree with Fred. Make a knife for a reason and it will be joyful. Sounds a little like a motivational speech, but it is true.
As far as getting yourself going, do this:
Set a time for getting out into the shop. Get up a half-hour earlier, wash your face and go out and just tidy things up, saw off a piece of steel, of profile a blade. You will be looking to get back in the shop after work or on the weekend to finish the job. ( don't loose track of the time and be late for work).
Draw a knife on a sheet of paper, cut it out in cardboard, cut it out in steel ( or forge it if you forge), grind the details in and finish the knife.
Have a knife making friend come over to help or watch. Teaching is the best way to learn.
Go visit another makers shop or attend a hammer-in or show. That usually gets the creative juices flowing.
Have fun.......Knife making shouldn't be a chore, it should be.....well....FUN.
Get more sleep, play less video games, turn off the computer.Being tired or mind dazed will made you depressed and not interested in doing anything.
Get more light, Seasonal Light Disorder is a real problem, especially up in your latitudes.
Silly as it sounds, a trip to a tanning booth (I actually hate tanning booths) may perk you right up.
Eat healthy meals, avoid snacks, take vitamins.
Hope you get going soon - Stacy