I've joked for many years that I think of parenting as "a slow death to self".
The death to self part (or maybe, less dramatically, a minimizing of self) is obvious : as a parent, your own "needs" & desires shuffle down a little lower on the list of importance when you have a dependent. (With the notable exception of that oxygen mask on an airplane, where I'm told you're supposed to put yours on first!).
The "slow" part is maybe a bit more arguable... When a child arrives in a parent's life, things change pretty quickly! But, in my experience, it has overall been a slow process of giving myself up for others, with acute times of change that are particularly noticeable.
Nap shifts (two-a-day to one, or one to — gasp — none) were brutal, like a mirror to reflect how much I cherished "my" time without my beloved's interruption.
Switching from being an advisor to a cheerleader is a wise & healthy, but nonetheless self-sacrificial, shift.
And right now, I am in one of those acute times of painful death... in this case, the death of my kid-free evenings! For one, I have a pre-teen who is a certified night owl. Futhermore, I find summer hours (late sunsets, warm evenings, plans with friends, nowhere to be first thing in the morning) make it really tricky to get kids to bed early in the evening. Or really, at any time that would be considered "evening"!
"Death" sounds bad, but overall, I think it's a good thing! It's been very inconvenient for my do-what-I-want nature, but it has been on the whole, major gain.
For me, being a parent has worn down some of my selfishness and smoothed out some of my hard edges. All of that makes me a better human, I think — with more to contribute not only to my kids, but to my friends, to my work, and to the world at large.
But, oof, sometimes it stings!