I assume that otherwise you feel none health-related issues, and it's just the "work-mode" that's affected. I also assume, that it's not a personal discipline i

I assume that otherwise you feel none health-related issues, and it's just the "work-mode" that's affected. I also assume, that it's not a personal discipline issue, that is you usually have no problem following your own plans to completion. Have you tried just letting yourself not doing it (whatever kept you at the desk) for some defined time (a day/week)? If this is affordable (wrt deadlines or income), then after awhile you may get bored with the not-doing and may feel the draw to get back to work on it again (thanks, the personal discipline). Another thing I'd try would be to see if there's some subject blocker there, either specific to what you currently study or more general to the direction of your studies. It may help just to talk to fellow students about a course/topic, or to a prof, even TA at the tutoring sesssion about your thoughts re direction of studies. Most people have had this sort of blockers at some point in life, different experiences, different solutions, but common feeling at the time. And, of course, a universal advice. Get in tune with your animal nature - sleep well, eat well, take walks outside (rain or shine), use your body as designed, the mind will recharge!