However, this exercise is about building a Rule of Life, about finding things that are good for us, healthy for us, that make us better able to serve God and serve others. And sometimes, saying "no" will allow us to be in a better frame of mind, in better health, and in a better spiritual place to then be able to say "yes".
Setting boundaries, learning that you don't have to try to please everyone all the time - these are very difficult lessons for some people. Here's a collection of articles that might be able to help.
Look at your schedule. Look at some of the things you already know are good for you - are some of the things in your schedule interfering with your ability to do the things that are good for you? Things like exercise, preparing healthy meals, getting enough sleep, etc. Where do you need to say no? And what do you need to clear away so that you can say a health "yes" to?