Am I a nut for feeling guilty about this?

I have a 3 year old cat who loves to play and has tons of energy. Some days I work all day and just want to go to bed, but I feel bad because she's so wild around that time (10pm) and just wants to run around and play. She loves chasing shoelace etc, but when I'm tired and I just want to go to bed, I don't feel like running around with a piece of string. I have this leveler for carpentry and it has a little laser on it, so when I'm tired I just sit there and let her chase the laser. I feel really bad because she always chases it but she knows she'll never catch it, and I'm not sure if she's having fun chasing it or is just getting mad and frustrated. I know I sound silly but am I doing her harm?