Don't compare your back-of-house with others' front-of-house.
Usually, we only see others' front-of-house, and because we know all about our own house it's easy to find ourselves comparing how we're doing in the back with how others are doing in the front. Often a recipe for unhappiness.
I remember wondering how a friend was so calm before their first child. They said, "I'm like a duck, calm on the surface, but underneath my legs are kicking like crazy."
The truth is we don't know how others are doing so best not be comparing at all.
This idea is inspired by an exercise about the hidden parts of parenting from The Book You Wish Your Parents Had Read by Philippa Perry, though I'm pretty sure as a metaphor it can be quite widely applied.