The single dumbest investment observation I ever heard came from a portfolio manager for whom I once worked. 

An otherwise intelligent and erstwhile fellow who at the time was in his early thirties, he said that this was a business - equity portfolio management - where age and experience was a hindrance. 

In one way, he had a point.  It was 1999 and the Tech Bubble was in full throttle.  The observation was true, if one chose not to participate in the insanity of The Talking Sock Puppet Era, when all the wise twenty- and thirtysomethings saying that the Gray Hairs just "didn't get it."  Many if not most of those wise before their years "didn't get" their paychecks for much longer.

(The second dumbest thing I ever heard came from a strategist at a Bulge Bracket firm who said - also in 1999 - that rising interest rates and oil prices might hurt other stocks but not tech stocks because technology companies "did not borrow money or use much energy."  That strategist is no longer with the firm.)

I have always revered the Gray Hairs.  Even though I am of that generation of which so many got sucked into the vortex of mass stupidity, I understand that there is no substitute for experience.  Give me a reasonably intelligent Gray Hair who has seen it all over the 30 year old rocket scientist with a Ph.D. from MIT any day.  The Gray Hairs won't draw false comfort in the indecipherable math that only 83 people in the world can understand, then blow your head off, as the rocket scientists so spectacularly have over the past year.

Bob Ferrell has seen it all.  The former strategist at Merrill Lynch offers 10 lessons he has observed after spending decades in the market.

1. Markets tend to mean revert over time.
2. Excesses in one direction will lead to an opposite excess in the other direction.
3. There are no new eras - excesses are never permanent.
4. Exponential rapidly or falling markets usually go further than you think, but they do not correct by going sideways.
5. The public buys the most at the top and the least at the bottom.
6. Fear and greed are stronger than long-term resolve.
7. Markets are strongest when they are broad and weakest when they narrow to a handful of blue-chip names.
8. Bear markets have three stages - sharp down, reflexive rebound and a drawn-out fundamental downtrend.
9. When all the experts and forecasts agree - something else is going to happen.
10. Bull markets are more fun than bear markets.

Given Ferrell's observations, the current bear market has a ways to run.

Via The Big Picture.