Many, many women, probably most of us, stop having babies while still longing for more. Among all my lifelong acquaintances, there are far more women who would gladly HAVE more children, but realize their families and/or circumstances can't reasonably accommodate them. (Nor can the world sustain the rising human population for much longer – many scientists and social scientists worry that we've already reached a tipping point that will affect future generations harshly.)
Longing will probably always be there to some degree, rising and falling with hormones and social pressures. But you CAN shift your attention. Ah, the many, many blessing of a smaller family! You CAN decide not to dwell on what you don't have. This is the "secret" to contentment of all the women I know who would gladly be pregnant again, and again, and again…, and yet are content and joyful with what they do have. Contentment is a state of mind, and to a very large degree, it can be chosen.
Our minds can override just about anything our bodies tell us. If not, people wouldn't be able to to diet, to run marathons, to overcome crippling accidents, to surrender needed sleep to meet the needs of a new baby, to quit addictive habits. Choosing to override your longing for another baby is one of the things your mind can do, if you decide to. It's your choice.
A final observation: Contrary to the "common wisdom," I have known quite a few moms (and dads) in my 60-some year who ended up regretting having more children. Health problems in parent or child, a change of circumstance, financial stress, a divorce, loss of job or home, even a neurologically challenged child have been contributing factors. These moms and dads loved all their children, of course, but nevertheless, in quiet, honest moments, wished that one of those children had never been born – a terrible emotional burden for the parents, and often for the child, as well.
And speaking of effects on the family, I hope you will never, ever hint to your two amazing little girls that they are not 'enough' to make you happy. They are if your focus is in a healthy place.
My best to you.