Article in English: Spend some time thinking about why you are considering investing in stocks. Are you investing to build an emergency fund for the future, to buy a home, or pay for college expenses? Are you investing for retirement?  It's a good idea to write out your motivation. Try quantify it in dollars, considering how much money you need for your goals. For example, purchasing a home might require a down-payment and closing costs of $40,000. Retirement might cost $1 million or more. Most people have more than one investment goal. Those goals often vary in priority and timing. For example, you may want to buy a house in three years, pay for a child’s education in fifteen years, and retire in thirty-five years. Documenting your investment goals will clarify your thinking and help you focus on the goal. Your investment goals will determine the time during which your investments will remain in place. The longer investments can stay in place, the greater the probability of positive returns.  If your goal is to have money to buy a house in three years, your time frame, or "investment horizon" is relatively short.  If you are investing to fund your retirement 30 years from now, your investment horizon is much longer. The S&P 500 is a collection of 500 of the most widely held stocks. There were only four ten year periods between 1926 and 2011 where the S&P 500 as a whole produced a loss. For holding periods of fifteen years or more, there were no losses. If you bought and held these stocks over the long term, you would have made money. By contrast, holding the S&P 500 for just a single year would have produced a loss 24 times in the 85-year period between 1926 and 2014. Over a short period, stock are extremely volatile. As a consequence, investing for short time periods is riskier than investing for longer time periods. You can gain more if you've invested well. You can lose everything if you've invested poorly. All investments have risks because there is always a possibility that you will lose some of your money. Stocks are no...

Summary in Vietnamese:
Đặt ra mục tiêu. Xác định khung thời gian. Đánh giá mức độ chấp nhận rủi ro của bạn. Tính toán các khoản đầu tư cần thiết để đạt được mục tiêu.