After Michael Harwell’s wife died of brain cancer two years ago, he learned to embrace the grieving process by relishing 56 years worth of memories from his marriage, and sharing them with friends.

Good news, bad news, a rough day, a scary movie, a poignant memory, a nostalgic smell—these are all things that can prompt a salty tear to trickle down your cheek. The sensation is quick to sneak up ...