It's the black swan, left field events - the "unknown unknowns" - that seem to cause investors most strife when it comes to successful investing.
When they strike, the masses run to the hills, screaming. They abandon their investment strategy without a second thought before finding the nearest cave (cash) to cower in, too frightened to come out for a long time.
This is the tragedy of many DIY investors, too arrogant to take advice yet too stupid to see the stock market's record for what it is.
They appear addicted to shooting themselves in the foot; they torture themselves and for what?
The record reflects everything - all the unknown unknowns along with all known knowns and known unknowns.
And that results are good and enough.
So why behave in a way that guarantees you less?