It's not that it's hard to say "No". Everyone can do it but what's hard is the feelings that come in the aftermath of saying no. Particularly guilt. But guilt doesn't actually come from saying no, it comes from what we think about saying no. When you change what you tell yourself about saying no, it becomes easy. When you reassure yourself that saying no is not only ok but necessary, you become someone who says no to things and yes to themselves.