My memory often fails me. But sometimes it hits me over the head.

That one-two punch — forgetting and then without warning, remembering — occurred recently. It was about 5 a.m. and I was reading a magazine on my phone in the darkness of my bedroom.

I had been awake for about an hour but it was too early to rise, so I was catching up on a variety of articles when suddenly it occurred to me: I had forgotten the birthday of a dear friend that happened about a month earlier.