It certainly does get better. My first had just turned 4 when #3 arrived (and 6 with #4, but a ripe old 9 when # 5 arrived). My Dh was away often and for long stretches. I just kept in mind mine was a volunteer position,and that it was up to me to take the days as the gifts they are and enjoy them. Not always easy (especially when someone is sick or really out of sorts) but it is fun. Very fun.
I don't try to be a mothering.com perfect mom ( if such a creature exists). I focus on the things that matter most to me (gentle discipline, learning, healthy eating, outdoor time) We are tv free, but not organic eaters, co-sleepers, tri-lingual yoga afficionados. We use disposable diapers
(a leftover from the days when we had no washing machine).
When I am feeling overwhelmed like OP sounds now I try to look at what I am doing to see if there are a few things I might let slide. It is more important to enjoy our days than it is to make our own yogurt (not that they are mutually exclusive but they certainly would be for me)!
Happy to have a new tribe to check in with!
