As women we are trained to do it all, and to make it look effortless. Of course, we all know it's not that easy. In fact, it's impossible. But nobody's talking about it. We compare ourselves to other women who appear to have it all together and tell ourselves that we need to do the same.
The world will suck our souls dry if we let it. There will always be demands on our time that are worthy causes, but does that mean you need to say yes? My husband once told me that just because there's a sale doesn't mean I need to participate. And a friend once told me "Just say no to volunteering" when I was completely overextending myself. At one point I attempted to quit a part-time contract I had on the side and left the meeting having volunteered to take on more responsibilities. Ugh, saying no is hard.
Why is saying no so hard? The story I often tell myself is that I'm letting others down if I say no, but I don't think that's necessarily true. I think the real reason it's so hard to say no is that we feel inadequate to not play the role of "good girl" who is uber compliant and says yes to everything.
It's not only your right to say no, it's your responsibility. Nobody else is going to protect your time and energy; therefore you must do it yourself. You can't be effective in your various roles when you're overextended. You also need and deserve life balance. That means time for work AND play.
Practice saying no to some little things at first. You'll find that it's not so awful. As you gain confidence you will find it easier to say not to bigger things. Setting boundaries is healthy, and no is a very powerful boundary.