Ow, my head hurts

For one thing, if you get too much sleep, it generally leads to your head feeling rather sick.

For another thing, staring at a computer screen almost 12/7 will do that to you.

And finally, I have found that if you hear a person talking Russian, which you are just beginning to understand, and you are trying to figure out what they are saying, it can lead to a very draining overall experience.