I found it incredibly difficult to say no. I hate to disappoint people, and would rather try to do many things all at once than say no to other people. When I am unable to make an event, I feel a lot of guilt about it, even if it isn't my fault. During the Christmas holidays, I had to cancel plans with a friend because I was sick, and I felt awful about it. So you can tell that I hate saying no to people.
I've been told that I do a lot, but I always think, I could do more. There are still days where I have no tasks, no things to go to. There are still points in the day where I don't have to rush around to go and do something. If I sit and just watch TV, or just read a book, I hear thoughts in my head saying 'you're wasting time when you could be doing something useful'. I never thought that I had a problem, until I met someone worse than me. Its funny how an outside perspective gives you a rational thought that the person is doing too much, but you don't apply it to yourself. Saying no is difficult, especially when society has conditioned you to want to say yes. Saying no has a negative connotation in society. If you say no, then you're not open to change, or new experiences.
It is something that I had to learn to do. Make my priorities and stick to them. If I commit to one thing first, unless it is an emergency, do not try to do too much at once. Concentrate on the things I am doing, and do them well. And do you know what? It was such a revelation. It is very liberating to say no to someone just for the reason that you can't do it. It's too much work, or I am simply unable to make it. Or just say that I don't want to, that it is not my thing. I'm not going to turn down an opportunity, but I will be clever about it. I will do as much as I can, but I will not stretch myself too thinly or allow myself to burn out. Days off are good. Just not quite as good as days where you get a lot done.
Try it. Say no to someone you wouldn't normally would, unless you actually want to do it. Don't just go along with something because everyone else wants to, or you think you 'should' do it.