Subatomic: When a force is applied in one direction it meets an equal force coming at it in the opposite direction. This could be applied to the the things we do.

Forces always occur in pairs of the same type of force, and it is not possible for one object to exert a force without experiencing a reciprocal force.

Everything we do is meet by something apposing it in the opposite direction. If I do a worthy deed, an equally worthy deed is likely to meet me in the opposite direction.

Reciprocity can be summed up like this: when you act on things, they act on you.

Sometimes bad thing happen to good people who do good things for others. When relating Newton's Third Law to the messy human realm things are not perfect but they are nearly so and will help produce better outcomes in life.

Forces always occur in pairs.

Two type of reciprocity

“I help you and you help me.”
“I help you and then you help someone else.”

Reciprocity is about playing the long game of win-win.