>>76520840 (OP)
you stop giving a fuck. Even good results don't improve mood. Instead of celebrating or feeling proud about stuff you just feel completely empty inside. You do the motions of going to work, lifting, etc. and immediately come home and rot alone for days straight.
In the gym you notice your stamina is shot. 3rd set feels 10x harder even after a rest day. Also the pump is suckier
All you can really do is go "fuck it" and hang out with friends, take a week off from lifting/studying, etc. Catch up whenever, it's not current you's problem.