"If this isn't nice, what is?"

I recently came across this Kurt Vonnegut passage:
(via Austin Kleon, whose books I've highly enjoyed)

"My uncle Alex Vonnegut, an insurance salesman who lived at 5033 North Pennsylvania, taught me something very important. He said that when things are going really well we should be sure to notice it. He was talking about very simple occasions, not great victories. Maybe drinking lemonade under a shade tree, or smelling the aroma of a bakery, or fishing, or listening to music coming from a concert hall while standing in the dark outside, or dare I say, after a kiss. He told me it was important at such times to say out loud, 'If this isn't nice, what is?'
I urge you to please notice when you are happy, and exclaim, or murmur or think at some point, 'If this isn't nice, I don't know what is.' "

This thought has been strumming through my head lately.
Yesterday, on a warm sunny spring afternoon that brought me to Central Park with my daughter, I had to repeat it a few times.

Can you blame me?
We sat underneath these branches and ate lots of crackers and watched dogs and other babies and everyone come by. Most people had to take a few pictures, too.