From “Having Kids,” by Paul Graham:

Partly, and I won’t deny it, this is because of serious chemical changes that happened almost instantly when our first child was born. It was like someone flipped a switch. I suddenly felt protective not just toward our child, but toward all children.

You will have chunks of time to work. But you can’t let work spill promiscuously through your whole life, like I used to before I had kids. You’re going to have to work at the same time every day, whether inspiration is flowing or not, and there are going to be times when you have to stop, even if it is.

I’ve been able to adapt to working this way. Work, like love, finds a way. If there are only certain times it can happen, it happens at those times. So while I don’t get as much done as before I had kids, I get enough done.

I hate to say this, because being ambitious has always been a part of my identity, but having kids may make one less ambitious. … The fact is, once you have kids, you’re probably going to care more about them than you do about yourself. And attention is a zero-sum game. Only one idea at a time can be the top idea in your mind. Once you have kids, it will often be your kids, and that means it will less often be some project you’re working on.