It begins before your child can even talk. One moment your contented little baby is cooing happily in your lap at playgroup, then along comes a crawling thug-in-the-making who swipes whatever your child is playing with, and before you know it you're leaping just a touch too assertively to the defence of your little darling.
I've seen it happen countless times. It only takes the tiniest of threats to the happiness or wellbeing of our kids and suddenly - without warning - our inner lioness is unleashed.
But when should you start repressing that instinct to defend your own, and when is it more appropriate to let your kids fight their own battles?
I was a test case in this recently, when my son came home and repeated some pretty vicious things another child had said to him at school. In the grand scheme of things it wasn't a big deal - certainly not worthy of flagging up to the Principal - but nevertheless, my ire was well and truly provoked. It was an act of cowardice rather than bullying - just some mean-spirited words clearly intended to wound.
But the injustice of it all really got to me. This other kid's nastiness had gone unchecked while my son sucked up the mean words and moved on. If only I could have done the same so easily. But no, I was all set to march up to the school to have it out with the kid in question.
My son was obviously mortified by my reaction, so once I calmed down I resolved to discuss it calmly with his teacher. But even that was unacceptable to my eight-year-old, who wanted to deal with it his way.
Admittedly I was still tempted to have a quiet word with my son's teacher behind his back, or even to raise it with the child's mother if the opportunity presented itself, but I decided to respect my son's wishes and just butt out.
And, as I should have known, he dealt with it brilliantly without my input and the whole thing just blew over.
Naomi Richards, a children's life coach and author of The Parent's Toolkit, says it's vital for parents to grasp whether their kids are asking for help with a fall-out with a friend, or whether they just want you to listen while they talk through what's happened.
"Ask your child if they want some input from you," Naomi advises. "Do they just want you to listen and nod your head, or are they asking you for solutions? If so, give them a few ideas for how to get their friendship back on track, and discuss with them which ideas they think might work.
"They know their friends and what they might be receptive to. Above all, parents should only step in with the agreement of the child."
That's a sentiment shared by mum of three Cara, who learned from bitter experience that fighting your kid's battles on their behalf can sometimes go horribly awry and end up making everything worse.
"Leave them to it and don't get involved," Cara says. "Chances are the kids will be playing together again by lunch time, whereas if you intervene in your child's fall-out, you run the risk of having to deal with parental huffs and grudges forever."
I dread to think how much more drama my interference would have created. So I learned my lesson, and my kid felt heard and respected. Meanwhile his friendship with the kid who had been mean to him at school was salvaged, and he had the added satisfaction of knowing that he's perfectly capable of holding his own in the playground, and can fix his own fall-outs by himself.
I think that's what you call a win-win scenario.