You just need to be organised about it, like if you got homework due or an exam you gotta study only you know how long you need to study for but if you start early enough you can find time within the studying to do other things but if you're constantly behind in studying so going from 1 thing to another you're never gonna have time to do both. You also have to realise that if you wanna do all 3 either gaming or social life time has drop a bit.
Edit: what you're feeling is completely normal and trust me everyone you think is managing all 3 is failing at 1 of them (or they're dogshit at games)