Question about ADD and medicine?

Alright, I take vyvance 60mg and unlike other people I have never had any side effects to it. But that's not really what this is about. I'm almost out with this prescription and I was thinking about just laying off it at least until college starts up. The reason it has taken me so long to want to go off it is because of how I act when I go off it for day or two. Basically when I'm off of it, I don't have much energy. I feel like a slug and just don't have motivation to do any work. I just want to sit on the couch and play video games or get on the computer. But when I am on it, I will do any yard work i need to or anything. SO... if I am off it for a while and let it get out of my system, will I go back to acting normal and have my regular energy back? I'm guessing the only way to know for sure is to just quit taking it and see?