It me hard that way too when I first read it, May. (The book is called Non Violent Communication, if you're interested). What made the difference to me was understanding the difference between a request and a demand. A demand has consequences. There's always an unspoken 'or else' in a demand. When someone demands something of you, you know it. When they request something, you feel free to enact your boundaries in a way that is good for you, say no safely or say yes totally freely. It makes giving altruistic, rather than bargaining.
Anyway - it really transformed how I speak with my children and my H - and while it hasn't changed the way he speaks to me, it has changed the way I listen to him. I can often hear, under his grumbling, a very simple request for care and attention. At other times, a demand that I take the blame for his feelings. When he is requesting care, I give it. When he is demanding I accept unreasonable criticism (because it makes him feel better) I step away. At least he knows - I hope - that when I give him care it is given freely, and because I want to, not because I am trying to manipulate him out of a bad mood so he will be nice to me.