I think for us it comes down to three ideas:
1. Choose my battles / let go of the unnecessary control struggles
My eldest will struggle for control at every turn. When she was younger, I'd get emotionally involved in our 'battles' and wouldn't step back from the unnecessary conflicts.
Interestingly, the trick with her is to give her responsibility along with freedom. For example, rather than struggle over clothes, I keep two simple guidelines: They have to be weather appropriate, they need to be appropriate per our activities (we don't wear our nice clothes to paint or climb trees and we don't wear dirty or torn clothes to town).
She has her own system to sort and store clothes (one that she came up with and that works for her), is responsible for folding and putting away clothing, and gets herself dressed in the morning without interference.
No. More. Struggle.
Likewise food. When she helps in the kitchen she eats more dinner. She'll wash lettuce, cut mushrooms, stir sauce...and suddenly she wants it.
I let her negotiate, but if she whines or throws a fit, it's a no go + consequence. You can discuss it with me and also, if I've heard your case and say no, then you drop it. She likes helping and to feel like a big kid. That was as true at three as it is at five. Just took me a little while to figure that one out.
- Find a place to channel the wild energy
Both my children are very energetic people. Getting them to sit still is an exhausting task. I have to run them out. Bike trails, open stretches of grass, games meant to keep kids running (the entire time) fresh air rain or shine, social activity, playground time (great time for me to sit and read a book or daydream because THEY go-go-go and I can let them have the space to do it) - if hours of our day aren't spent outside and kicking up dust, they become monsters.
- Consistency + Flexibility (seems like maybe they'd be at odds but in fact the two are made for each other)
There is a time and a place for everything. We have conditional rules, yes. We don't, for example, just on furniture at Nana's house. We do at home. We don't sing loudly in a library. We do at home. We don't run at the pool. We do outside (well, and inside when it's nasty outside...we also roller skate, obstacle course, dragon hunt, etc. inside 'cause it rains a LOT 'round these parts). We don't touch the walls at grandpas. We do at home. We don't eat dairy at H.'s house. We do at P.'s house. So, I teach environmental analysis and behavioral adjustment rather than black and white rule following. Can't tell you how many times I've answered a question with, "Different rules for different people at different times."
Also, some days go just as I planned (okay, not very often). Other times I have to live life of life's terms. You got wet at the beach and are cold? Okay, we're going to need to stop by the car and change before we go to the doctor. Not a big deal. We get wet and muddy.
Oh, which also leads me to preparedness. Now, if I were organized I'd probably keep a magic-bag-of-all in my car with snacks, dry clothes, money, water, books, toys, crayons, etc. Instead...My car is this overflow zone that encapsulates all of the above (and more) but without any organization. Need a toy? Check the floor. There's a towel...somewhere in the back. Right under the squirt gun. Which is under the granola bars. With is under the umbrella that we made into a jelly fish costume last year (no joke). When I clean my car everything goes haywire 'cause I loose my emergency supplies!
Someday I'll be prepared AND will be organized. Sigh. Someday.
In the meantime it really does help to have supplies on hand. I keep liquid, snacks, first aid, a few random toys, etc. on hand in my backpack. The rest hangs out in the car. That way I don't have to say no as often as I do if I'm just sticking to plans. Heck, if we have time to stop and pick blackberries on the way to the dentist, why not stop and pick blackberries!
Honestly, it sounds like you got this. You sound like a really sweet and safe mama. Good luck keeping up sister!