I am feeling very drained and tired

It's my first day, I have been nicotine free for about 6 hours. The problem is, and this has happened before. I can hardly keep my eyes open, I am feeling very drained and tired. Yet, my arms and legs just want to move, I have a strange feeling that I need to move around and walk some, but at the same time I am finding it really hard to keep my eyes open. I am not smoking again. This is the day I quit for good. Was just wondering how long am I going to crave for and how long will I be this tired?