Compounding is what Einstein described as the most powerful force in the universe. You can observe compounding effects in personal life, business, knowledge acquisition, experience, society, and physics.
For the purposes of behavior, Peter Kaufman's description is sufficient - dogged incremental progress over a long period of time. Be constant, not intermittent.
There is a problem with inconsistency - variance drain. When you interrupt consistent increases above a certain threshold you loss out on the critical mass and step down a level. Think of pushing a boulder up a hill and stopping before you get to flat ground.
Questions - Happiness is an investment portfolio that benefits from compounding interest. Your "blue chip" investments should be quality relationships, a mental training / spiritual practice, an exercise program, getting better at work you enjoy. What are examples of variance drain in happiness habits?
Connections - compounding depends upon discipline 3,