No one knows the weight of another's burden.

A hardship may weigh more heavily on the person experiencing it than others realize. Its outward appearance does not reveal its full effect.

The proverb encourages humility and compassion rather than confident judgments about how easily someone else ought to cope.

Use it when someone is minimizing another person's difficulties or assuming they should cope more easily. It can also encourage patience when a struggle is not outwardly apparent.