Hey there @SnowySoph 
Yeah completing schoolwork and studying at the same time is very mentally draining, especially when it is very important to your future.
I had a time during my first and second year of university that I wanted to stop and to take a break because I started to feel mentally tired, but the more I went into the course that I didn't want to waste the efforts I have placed into completing the course.
But experiences of completing studies are very personal and differ from person to person, So before thinking of wanting to withdraw, can you try to think of the reasons why it has been taking a toll on you mentally? And is there ways for you to relax and recharge yourself, so that you won't feel mentally tired?
I hope this will help you!