All markets look liquid during the bubble (massive uptrend), but it’s the liquidity after the bubble ends that matters.

Markets tend to over discount the uncertainty related to identified risks. Conversely, markets tend to under discount risks that have not yet been expressly identified. Whenever the market is pointing at something and saying this is a risk to be concerned about, in my experience, most of the time, the risk ends up being not as bad as the market anticipated.

Traders focus almost entirely on where to enter a trade. In reality, the entry size is often more important than the entry price because if the size is too large, a trader will be more likely to exit a good trade on a meaningless adverse price move. The larger the position, the greater the danger that trading decisions will be driven by fear rather than by judgment and experience.

Virtually all traders experience periods when they are out of sync with the markets. When you are in a losing streak, you can’t turn the situation around by trying harder. When trading is going badly, Clark’s advice is to get out of everything and take a holiday. Liquidating positions will allow you to regain objectivity.

Staring at the screen all day is counterproductive. He believes that watching every tick will lead to both selling good positions prematurely and overtrading. He advises traders to find something else (preferably productive) to occupy part of their time to avoid the pitfalls of watching the market too closely.

When markets are trending up strongly, and there is bad news, the bad news counts for nothing. But if there is a break that reminds people what it is like to lose money in equities, then suddenly the buying is not mindless anymore. People start looking at the fundamentals, and in this case, I knew the fundamentals were very ugly indeed.

If you don’t understand why you are in a trade, you won’t understand when it is the right time to sell, which means you will only sell when the price action scares you. Most of the time when price action scares you, it is a buying opportunity, not a sell indicator.

Normally, I let winners run and cut losers. In 2009, however, as a result of the posttraumatic effects of going through the September 2008 to February 2009 period—talking to clients who are going out of business and seeing 50 percent of your fund redeemed is all very wearing—I got into the habit of snatching quick 10 to 15 percent profits in individual positions. Most of these positions then went up another 35 to 40 percent. I consider my pattern of taking quick profits in 2009 a dreadful error that I think came about because I had lost a degree of confidence due to experiencing my first down year in 2008.

As an equity trader, I learned the short-selling lessons relatively early. There is no high for a concept stock. It is always better to be long before they have already moved a lot than to try to figure out where to go short.

Now that you have switched from net long to net short, what would get you long again? – Buying. If all of a sudden stocks stopped going down on bad news that would be a positive sign.