Tiredness is always a problem, you will focus on being tired and forget to absorb anything important. I found out when my time limit is to do revision, so after that time I either sleep or do something constructive which isn’t taking in information. Being awake can be much more beneficial, but some people can revise whilst being not entirely with it
Try and find other things to do as well as sleep, like plan the revision / work for the next day, as it doesn’t require taking in information and can be constructive instead of doing it when you are awake and “revision ready”
It's pointless to revise when you are tired, I am ALWAYS ****ing tired on school days so I usually take a long nap in the evenings and study for few hours during the night, no matter how hard you try you just aren't going to learn anything while you are tired.