Never Satisfied

I'm having a hard time telling if I'm perpetually unsatisfied, like in an unhealthy way, or if I'm simply ambitious. I've never held a job for more than 2 years, and generally by the 1 year mark I'm trying to figure out what I'm moving on to next (I'm 26 so I've only had 3 "big girl" jobs). I've also lived in three different states since I graduated college. I'm now at the point of my life that I really want to start a family and I'm feeling impatient. I just want to much more for myself and my family. But I don't want to be perpetually unhappy, getting what I want and then only wanting more. I'm scared I'll finally have a baby and be a stay at home mom, or maybe a working mom, and still not be satisfied. Is this normal? What can I do to teach myself to love the life I have? I know plenty of women would love to have a great husband, a stable job, paychecks that cover the bills! Shouldn't I just be able to be thankful?