How to beat my intertia?

I think that studying too hard can make you feel drained.
You should probably give yourself more time to switch off or do things that you enjoy to recharge your batteries.
Maybe you just got to a stage where you are telling yourself to take some time out for yourself.

I had problem like you earlier. I've concentration problem with study. So i did few experiments with it. I used to study one chapter per 30 minutes(if it covers that much time) after that another subject. Just changing subjects kept my mind fresh and i was able to revise lot of things in less time. Also do have constructive hobby like painting, writing etc. It helps to relieve tension sometimes. And to work with inertia i can suggest you that, you should compete with yourself. Always self-evaluate, if you're happy with performance. Keep searching for better of yourself. use your failures and excuses for improvement. Always accept where you did wrong. This will help i hope.