Risk can be greatly reduced by concentrating on only a few holdings.
I think the worst mistake you can make in stocks is to buy or sell based on current headlines.
You don't ever ask a barber whether you need a haircut.
Diversification may preserve wealth, but concentration builds wealth.
I always say that in investing you want to buy stock in a company that has a business that's so good that an idiot can run it, because sooner or later one will. We have a country like that.
I do know that when I am 60, I should be attempting to achieve different personal goals than those which had priority at age 20.