a thing that I should learn

When a marriage matures, you can tolerate differences in each other. If she's social and he's a couch potato, it's okay for her to go out socially and for him to be home watching the ballgame. Each one is happy that the other is having a good time; and neither one resents the other.
That's generous love. Selfish love is when she drags him out or he keeps her home. But that's not really love: that's control.
It takes generous love to survive the large and small events of a long relationship. It takes generous love to keep listening to each other - and to learn from each other.