Why do humans always seem to desire MORE, regardless of how little or how much we already have?

I'm only 20, but I definitely know what you are talking about. Although I don't have a family (of my own) or a job, I still become depressed sometimes because I'm always wanting more. What I realized, though, is that I wasn't living for myself, but rather for everyone else in the world. I mean you are kinda stuck right now because you have kids, but I would just look at what you have right now and come at it with a whole new attitude. Instead of dreading waking up every day, you can take what you have and make it something new. Maybe you can talk to your husband about how you feel, because lack of communication in relationship causes a lot of deep frustration. You might be surprised as to what he has to say. you sound like a wonderful person, so don't let your life go to waste. Start doing some things that make you smile, and embrace every aspect of life as if you were the queen of the world and no one is going to stop you! this is YOUR life, always remember that.