I like to start a discussion I in the morning and then go to work so I have something to pop in on during the day. 
Ok, the other day I felt guilty because I was physically exhausted and so blew off sports day in order to rest before a busy evening ferrying kids about.
I felt guilty because I felt like it's wrong not to suffer any inconvenience or discomfort for even the most trivial of my children's pleasure. I "should" suck it up and stand around in the cold watching races just so my kids see me there. But, why? How is it really good for an exhausted mother with aching feet to do this? Isn't it better for mum to be rested and happy at tea time?
Obviously, some things are so important that you carry on, regardless. I didn't cancel a client in order to rest: the money is important to the family. And, if the event had been something truly important, then it would be a different matter. I would stand cold and aching if it was truly important to the child's well being.
I see a lot of threads on here from exhausted, miserable mums who are burnt out and resentful about their lives. Is some of that due to prioritising the family over their own well being?