Know returns will come eventually, but do not know how much and when they will come.

Markets are uncertain and unpredictable, and that is the price of admission to pay to be invested.

It is not just what you know, but more of how you behave that matters.

The last point is so key. Your discipline to avoid making emotional decisions is the most important long term factor of investing success, I truly believe that. Good habits take a long time to build, but can erase in an instant off of one irrational behavior move.