You can expect to be tired from practicing (working out) sometimes, especially in the beginning. If you're having trouble sleeping, your appetite is poor and your exhausted, you may be over-practicing (over-training) or at least over-reaching, and you should probably take a little time off.

If you are so sore you can't move then, again, you're going to need a some recovery time, but otherwise, some aching in your muscles is to be expected and is not a bad thing at all. You'll learn over time the different levels of fatique and soreness and how to respond.