exercise then and now

I was at cheer practice today and we were doing jumping jacks. I thought to my self, "jumping jacks have never felt like this before!". When we were little jumping jacks were the fun exercise just to jump up and down and have some fun. But, today I was really feeling the burn! Bicycles were never a problem either. I enjoy them still even today but they hurt lol! Maybe its because when we were little or when I was little I just did them for the fun and wasn't really trying to get in shape. I was a fireball as a child and had a lot of energy so I used it on exercise. I'm still a little stunned that jumping jacks ACTUALLY hurt today! Its really really weird because they never made my thighs feel like someone poured gasoline on them, lit a match, and then threw the match on my thighs to just watch them burn. I've always heard, "if it hurts then you must be doing it right". Is that true???? Hmmm well I don't know but what I do know is that jumping jacks aren't supposed to hurt to the point that my favorite childhood exercise is my not so favorite anymore. Hmmmm deep in thought about this lol.. I'm deep in thought about this small little thing which is the norm for me anyway! Well, I'm gonna go think about this here issue and catch you guys later =) adios