Well i can definitely tell when i've gone past my limit, normally it feels like theres pressure on my head especially on my sinuses. Yesterday i pushed myself a bit to hard and when i tried to go sleep last night it was awful. My eyes kept bouncing around and it was REALLY irritating. Finally after a couple hours they stopped and it felt like it was kind of hard to open them

I do however, always wake up feeling better than the day before. And if im on the computer frequently things seem to worsen up so im definitely going to be taking quite a few breaks throughout the day from now on. Last night kinda sucked.