Try to break down your work into little parts. See these parts as individual tasks. Mark them on your list when they’re done, you’ll feel satisfied, confident and full of energy to take on the next task. Even when I’m working on a 4 month projects, I split the project up in milestones (4 to 6) and these milestones into tickets (or whatever you want to call it) of half a day to 2 days each which you then again can split up into tasks. Make sure mentally demanding tasks are interrupted by simple actions (answer mail, check up on your colleague, breaks, write a manual, …). You’re going to notice the project isn’t as hard as you thought it was in the first place. Just minimize your goals (finish one task) and see them in perspective (the whole project).