Long-term investment success is almost totally a function of how one emotionally handles declines in the equity market, as opposed to how one's portfolio handles them.
Declines are temporary, gains are permanent.
Timing the market is a fools game, whereas time in the market is your greatest natural advantage.
Wealth is not determined by investment performance, but by investor behavior.
Investment performance doesn't determine real-life returns; investor behavior does.
Once you decide that mediocrity is unthinkable, your only choices are excellence and quitting.