It would be easy for me to comment something like "you got this" or "keep pushing," but that's impersonal and insensitive. Tiredness/fatigue is so damn real and when it comes to little projects/tasks, the effects are especially draining--mentally and physically. My suggestion is to take a day off. A full day of doing whatever it is you would rather be doing. Get to the gym, go for a hike, lay in bed all day, etc. etc. Give yourself some much needed relaxation and distress time. I don't know how far you are into the process, so maybe that's not a viable option. If a full day isn't plausible, take 4 hours of a day even. I have been put in very similar positions as this, especially during finals week. Sleep. Destress. Recuperate. Begin again.