Personally, I think the notion that women, particularly moms, had to be superwomen came from our moms plus our own generation's belief that we could have "it all," whatever "it" was. Our moms were raised to take care of house and home so that the dad only had to focus on providing for the family. Then, our generation wanted career and family and struggled to find the balance. Well, the balance is achieved when partners chip in as equally as possible, not just when you distribute your time equally among the dozen-plus roles you play daily. "Superwoman stress syndrome" was a popular subject of study in the 1990's, and by the turn of the century, women realized that it was not a sign of their weakness to say "no" or ask for help with house and home without fear of being seen as "failures" in some way.
Like you, I was fortunate to have a husband who was willing to help with our brood of three, and my mom nearby to offer occasional relief. Remember, too, to take a little time out for yourself. Life is far too short to stress over things that don't matter, and stressing out prevents us from appreciating what's important. Just admitting that it's okay to not have to do it all is a huge step in a more fulfilled life. Congratulations!