If I had to pinpoint one thing that made my life as a parent easier, I'd have to say it was my university course in developmental psychology. My kids always said Mum always knew what phase they were in before it happened! It's comforting to know that these phases are completely normal, that they occur for a valid reason, and that they will not last forever. If you haven't taken this course, seek one out. Or buy the text book and devour it.
Other than that, I guess my best advice would be:
Choose your battles carefully. If the outcome won't matter 20 years from now, it probably doesn't matter now. If it will, then it does, but you don't need to win just to prove you're the parent.
Hold them very close then let them go. Protect them when they're too young to make good decisions for themselves, but gradually give them the freedom to become their own persons. Helicopter parenting isn't doing the kids any favours. They need to learn how to navigate the world.
Don't negate their feelings. Allow them to experience sadness or defeat. Let their feelings wash over them, without saying, "Don't be sad" or "It didn't matter that you didn't get that trophy" or "She wasn't worth it anyway". They have to learn to trust their own feelings. Commiserate with them, though. "I'm so sorry you feel sad" or "Honey, I'm sorry your team lost" acknowledges their feelings without negating them.
Teach them manners. You may not think they're "getting it" but they are, and it will show in time. Every time my son pulls out my chair for me, I thank myself! LOL.
Use humour to sugar-coat your parental rules. It helps the medicine go down. "Oh, go ahead. Humour the old bag" and "Because I'm bigger than you are and I can beat you up" were two of my go-to remarks when my kids questioned my requests. The latter, I should add, was a big joke because I never even once spanked my kids!
Make chores a game when they're younger. I was reminded of this on Easter weekend with my granddaughters. I asked them to pick up the straw from their Easter baskets. They ignored the request. After a few minutes, I got a couple of empty baskets and said to them, "Can you see how much straw you can collect?" Then it became a game. When they brought their baskets back (and every single bit of mess was gone from the floors!!!!), I rewarded each of them with an extra Easter egg. This is an example of what my own kids now call "sneaky Mumsy".
And above all, touch them. Human touch is therapeutic. Hug them a lot; one can NEVER have too many hugs. Smooth their hair. Rub their little backs when they're going to sleep. My daughter still sometimes asks me to rub her back when she's nodding off!