The curse of coming back

Why is it always so hard coming back?
My season hasn't even started yet, as a matter of fact it starts tomorrow but since the school has been open already for a week I had the opportunity to take some classes so I can slowly get back into shape, but dear Lord! it hurts. The problem is that I don't understand why. It's not that i have been sitting on my ass the whole summer without doing anything, no. I have been trying to exercise and keep an active profile during the summer without compensating having fun and still enjoying 'a summer'.

The muscles in my back are the first ones to suffer coming back to taking classes and rehearsing. Every time I try to do an arabesque it starts good. I even get a half a smile in my face as I look in the mirror. Damn! I'm feeling flexible. But is when that happens and you try to push it a little harder that i get the craziest cramp on my lower back. Why did I push? Why now?
Another interesting thing that my body does when coming back, happens during jumps. I had a good barre and an 'OK' beginning of center -Let's not talk about my pirouettes because I think my body forgot how to turn and how to spot- so my dizzy self listens to the simple petit batterie combination and gets ready in cinquieme position. I go ahead and leap toward the first sauté: first, my elevation from the floor is basically non existent, and sencond... the landing. It feels as if by magic my body has forgotten that I should easily land so I look and feel like a plane landing after a cumulus of turbulence clouds and I hit the floor if the hardest way possible. Ouch!
My feet are hurting now but because I am a dancer I keep going through the combination until I finish one side. After that I simply have to stop and I basically can't jump for the rest of the class.

Sometimes I think I am a weird person but this are some of the things that happen to me in the first, second and third classes I take after a long period of no dancing. Eventually it gets better but I always tell myself to go slow because I do have a fragile body that gets injured a lot if I don't take good care of it.