For me as a stepparent, I have a hard time letting go of my step daughters. Especially when it comes to "boyfriends".
And they are almost 27 and 30 years old. 🤦‍♀️

My guess would be protecting them or keeping them happy.

Just a guess, I'm not a parent.

Discipline. Definitely not something that I enjoy doing.

Seeing your child sick, or hurt. When they suffer their first heartbreak..it's awful. You then realize you can't protect them from everything.

Letting your kids learn from their mistakes

Maintaining discipline is actually easy enough. And there is not much hard things about being a parent.

But I'll tell you something else. One of the most DIFFICULT things ever is putting up with yelling, and lies told about you and sworn as true when it's not, and arguing with the children and passing it off as if they started it to begin with, and even suffering degradation and manipulation, like it's a curse or whatever, in which I speak from experience of. I mean read any of my stories and my "About Me" section, and you'll see what I am talking about.

Check this out for example:

https://similarworlds.com/1894405-I-Sometimes-Just-Wonder/2458093-Sometimes-I-wonder-if-this-is-true-or-not-if-what

Letting go.

Parenting within their flaws.