Diversification is a poor substitute for thinking.
Widespread fear is your friend as an investor, because it serves up bargain purchases. Personal fear is your enemy. It will also be unwarranted.
Consensus won't create great ideas. Basically, a good investment idea is pretty unusual and has to be a somewhat lonely insight. If the merit of an idea is visible to a lot of people, it quickly cuts into the price.
In the current up-cycle, over-weighted, liquid, large-cap stocks have benefitted from forced buying on the part of passive vehicles [e.g, index funds], which don't have the option to refrain from buying a stock just because it's overpriced.
Never will a man penetrate deeper into error than when he is continuing on a road that has led him to success.