If it is only once in a while you are unable to take your son to the playground, I am sure that it is ok. An off day once in a while is ok. If you are able to, then maybe you can do something fun at home, or watch a dvd together etc. I have had days like that with my son, when he was really too young to understand that I was not feeling well. So once in a while we had junk-food for dinner, pizza or whatever, and we watched TV to his hearts deligth that afternoon. It was a bit of a bonding-experience! Not super-mom, but nobody can be super-mom every day. I think it is important that children learn that their parents have needs too, and that sometimes they just have to accept that mom/dad are not feeling well. My son is a teenager now, and I miss the little boy he used to be. So try to enjoy him as much as possible, and don`t feel like you have to do everything perfectly every day. Most important is that he knows that you are there for him, and love him. That is what he will remember, not the days when you were unwell