Saying no

I've gotten really good at saying no.  I often say no--to my children, to my students, to my colleagues.  You see, I have to say no.  My life is structured in such a way that if I don't say no things don't get done.  I just said no to a colleague, a colleague whom I say no to quite frequently.  This colleague needs me to host a dinner for a visiting speaker as the colleague has a conflict.  S/he can't be two places at once, so s/he asked me if I'd relieve hir of one responsibility.  I said no.  It's an evening event, and given that I teach on Tuesday evening and that I'm guest lecturing for this colleague on Wednesday evening I have no desire to attend another evening event this week.  I just don't.  And I said as much.  My colleague was upset, and I do understand that.  But I can't do it.  More importantly, I don't want to do it.  I do the amount of service required of me, and I do it well.  I'm not up for taking on anything else.  I don't much care if I get the reputation as the person who says no.  I don't much care if people think I use my kids as a reason to not attend evening events.  I've learned the hard way that being nice won't get me very far at CU Land.  And I'm not going to feel bad or feel guilty for saying no.