If the answer is no then don't say yes

Don't say yes to someone when you know you have no intentions of doing it. An honest NO does far less damage. If you say yes then they stop looking for another way to get what they need done. If you would have just been honest and said no, they would have kept looking for a way to get it done. Don't say it if you don't mean it. There is nothing wrong telling someone NO. But saying yes when you know darn well that there is NO chance you would do it, is wrong. By the same token you can't overwhelm yourself with more than you can actually do by saying yes to everyone. If it is honestly more than you can handle then tell them NO, I would if I could but I just can't. You can't honestly say yes if the honest answer is NO. They may not like the answer but regardless they will appreciate an honest answer. If you tell them yes then keep your word. Like they say, A person is only as good as his word.