The paradox of the margaritas
Children are like margaritas.
Your first margarita of the day, like your first child, is a good thing. It improves your outlook and only slightly impairs your ability to operate normally.
Regardless of what your plan had been before you started, after the first one, a second seems more attractive.
Your second margarita begins to interfere with the way you usually do things. Accomodations are needed. You will probably need to adjust your schedule.
As your plans are already disrupted, there is that much less reason not to have another one. Although the incremental pleasure diminishes with each subsequent margarita, they still deliver joy.
Three is probably too many. But if you have already had three, there aren't many reasons left not to have more. You are no longer the same person you were before. You won't be returning to business as usual. And you are tempted by the exhilaration of having another one.
After your fourth, things get blurry. What the hell, have as many as you can afford! Have them even if you can't afford them! Worry about it later. Things will probably work out.
What is the optimal number of children? The answer of course is personal. But you can get close to the answer by asking yourself: How many margaritas are good?
If you prefer less introspective fare, my other blog is for the more practical and professionally-minded reader