If you have a written trading or investment plan, congratulations! You are in the minority, that's because most of the traders out there trade without a plan. While it is still not an absolute guarantee of success, you have eliminated one major roadblock holding you from being successful in trading. Trading is a business, so you have to treat it as such if you want to succeed in it. Reading some books, browsing online for tips on trading, buying a charting program, opening a brokerage account and starting to trade do not contribute to a solid business plan - it is a recipe for disaster. "If you don't follow a written trading plan, you court disaster every time you enter the market".
A plan should be written in stone while you are trading, but subject to re-evaluation once the market has closed. It changes with market conditions and adjusts as the trader's skill level improves. Trader should write his or her own plan, taking into account personal trading styles and goals. There is no way to guarantee that a trade will make money. Professional traders know before they enter a trade that the odds are in their favor or they wouldn't be there. By letting his or her profits ride and cutting losses short, a trader may lose some battles, but he or she will win the war. Most traders and investors do the opposite, which is why they never make money.