A stop-loss order is designed to limit losses on a position in a security. For long positions, a stop loss can be placed below a recent low, or for short positions, above a recent high. It can also be based on volatility. For example, if a stock price is moving about $0.05 a minute, then you may place a stop loss $0.15 away from your entry to give the price some space to fluctuate before it moves in your anticipated direction.
Diversification allows you to recover from the loss of your total investment (20% of your portfolio) by gains of 10% in the two best companies (25% x 40%) and 4% in the remaining two companies (10% x 40%). Even though your overall portfolio value dropped by 6% (20% loss minus 14% gain), it is considerably better than having been invested solely in company E.

In late 2014, legendary self-help and business guru Tony Robbins published a book called Money: Master The Game. In it he explains the strategies and ideas used by the very best investors in the world - hedge fund managers, asset allocators and billionaires - that he gleaned from them during four years of interviews and how their lessons should be applied by the rest of us.
The first stock market in the world was the London stock exchange. It was started in a coffeehouse, where traders used to meet to exchange shares, in 1773. The first stock exchange in the United States of America was started in Philadelphia in 1790. The Buttonwood agreement, so named because it was signed under a buttonwood tree, marked the beginnings of New York's Wall Street in 1792. The agreement was signed by 24 traders and was the first American organization of its kind to trade in securities. The traders renamed their venture as New York Stock and Exchange Board in 1817. (For related reading, see "The Highest Priced Stocks In America")
While both terms - stock market and stock exchange - are used interchangeably, the latter term is generally a subset of the former. If one says that she trades in the stock market, it means that she buys and sells shares/equities on one (or more) of the stock exchange(s) that are part of the overall stock market. The leading stock exchanges in the U.S. include the New York Stock Exchange (NYSE), Nasdaq, and the Chicago Board Options Exchange (CBOE). These leading national exchanges, along with several other exchanges operating in the country, form the stock market of the U.S.

Define and write down the conditions under which you'll enter a position. "Buy during uptrend" isn't specific enough. Something like this is much more specific and also testable: "Buy when price breaks above the upper trendline of a triangle pattern, where the triangle was preceded by an uptrend (at least one higher swing high and higher swing low before the triangle formed) on the two-minute chart in the first two hours of the trading day."
The idea of perception is important, especially in investing. As you gain more knowledge about investments – for example, how stocks are bought and sold, how much volatility (price change) is usually present, and the difficulty or ease of liquidating an investment – you are likely to consider stock investments to have less risk than you thought before making your first purchase. As a consequence, your anxiety when investing is less intense, even though your risk tolerance remains unchanged because your perception of the risk has evolved.

** Merrill waives its commissions for all online stock, ETF and option trades placed in a Merrill Edge® Self-Directed brokerage account. Brokerage fees associated with, but not limited to, margin transactions, special stock registration/gifting, account transfer and processing and termination apply. $0 option trades are subject to a $0.65 per-contract fee. Other fees and restrictions may apply. Pricing is subject to change without advance notice.

The biggest obstacle to stock market profits is an inability to control one’s emotions and make logical decisions. In the short-term, the prices of companies reflect the combined emotions of the entire investment community. When a majority of investors are worried about a company, its stock price is likely to decline; when a majority feel positive about the company’s future, its stock price tends to rise.
Imagine owning stocks in five different companies, each of which you expect to continually grow profits. Unfortunately, circumstances change. At the end of the year, you might have two companies (A & B) that have performed well so their stocks are up 25% each. The stock of two other companies (C & D) in a different industry are up 10% each, while the fifth company’s (E) assets were liquidated to pay off a massive lawsuit.
When you buy a stock, you should have a good reason for doing so and an expectation of what the price will do if the reason is valid. At the same time, you should establish the point at which you will liquidate your holdings, especially if your reason is proven invalid or if the stock doesn’t react as expected when your expectation has been met. In other words, have an exit strategy before you buy the security and execute that strategy unemotionally.
Rarely is short-term noise (blaring headlines, temporary price fluctuations) relevant to how a well-chosen company performs over the long term. It’s how investors react to the noise that really matters. Here’s where that rational voice from calmer times — your investing journal — can serve as a guide to sticking it out during the inevitable ups and downs that come with investing in stocks.