Feel like shit after quitting caffeine and L-Theanine

Hi, I've been using daily over the past two months about 300/400mg caffeine in combanition with ~600mg L-Theanine. I did this so I could get over with my 7 exams I had to write. Now I'm done and I'm currently on my holiday break, but I actually have to write a research paper during my break.

Since last week I have quit caffeine. I feel like shit, I have no motivation to do anything, I haven't written a single line yet. In my last holiday I had to write 2 papers, I did that shit in two weeks (working about 100hrs/week) on caffeine and L-Theanine, it's depressing to look back at that time and now I can't even write a single line after almost two weeks.

Idk what to do, how long will this depression last? Or should I just get back on it