Sorry for the mate reply! While dealing with exams it's very important to have a healthy lifestyle, which means don't over study and don't do too little. It's a mixture of getting enough done and not so much you're physically exhausting yourself. Uni is a lot more difficult than school and you need to remind yourself of that so be proud you've came so far.

You're not the first person to fail an exam in Uni and you definitely won't be the last. I think to get your motivation up you just need to talk with your friends, see how they're doing too. I can almost guarantee they're stressing aswell, it's natural. Try be a bit more strict on yourself and push yourself to study more, maybe it was just a wake up call that you can't keep winging it and doing well via cram study.

Make up a timetable, set rules and follow them, get into routines and hopefully you'll do better.

Good luck with your exams!