So, in Badminton, the point is to get the shuttlecock at the highest point and then swing your arm and snap your wrist. I don't know why, but I seem to have a huge problem lifting my arm high enough during games. In the drills, it's less of a problem, but during matches, my coach keeps on saying that my arm is so low it's like next to my shoulder. Any ideas on how to correct this? Cuz it's almost like a reflex now.
You'll have to correct the muscle memory to fix this. I'd say you should spend about five minutes of doing nothing but overhead clears with a friend per training session, at least, and focus on your technique and make sure you're hitting at the right point of contact. If you can get your coach to watch you do this, even better!
Just try the the following: Forget about swinging your arm for the time being. Just stand with your left foot slightly in front of your right foot, hold your racquet straight over your head pointing towards the ceiling and then just snap your wrist in a sort of shadow stroke without using a shuttle. Continuing with the shadow play, next try to do the same but this time with your right foot going in front of your left foot as you snap your wrist. More drills and you can then try the full blooded version in a game.
You need a better mental picture. Try practicising in front of a large mirror. I sometimes use a dance studio that has a mirrored wall.