The shopping cart has a preference for turning left. You would prefer to go straight. Neither of you is willing to compromise.
For the next twenty minutes, buying groceries involves a small but persistent wrestling match. It is inconvenient. It is also a little ridiculous, especially if someone is there to see the expression on your face every time you approach another corner.
A lot of ordinary humor lives at that scale. The bag described as “easy to open.” The piece of furniture that needs one final screw, now believed to be somewhere in the carpet. The confidently written note in your phone that says only “Thursday thing.”
Later, when someone asks how your day went, you might have very little news. You bought groceries. You wrestled a cart. In the telling, though, the cart starts to become the main event. The other person has met that cart, or one of its relatives.
Shared humor can be as small as sending a picture of the shelf you have just assembled with one panel facing backwards. It can be a running joke about a plant that has survived your care rather than benefited from it. The joke gets funnier when the plant unexpectedly produces a flower. Someone needs to hear about this development.
It is pleasant to have someone who knows the background. A picture of a flower is ordinary enough. A picture of that flower, sent to the person who helped you move the apparently dead plant into a better spot, comes with a history. You have both been following this deeply unimportant story.
The shared part matters. If someone is embarrassed by the joke or trying to tell you something painful, pay attention to that. Your own harmless miscalculation, a shared inconvenience, or an object with suspicious design priorities usually offers plenty to laugh about without making someone wish the conversation would end.
Most weeks offer an untidy mixture of serious conversations, ordinary chores, and things that are funny for reasons that would take too long to explain to anyone else. With the right person, you can move between them. They hear what is going on with you. You hear what is going on with them. Eventually one of you remembers to ask how the plant is doing.