Never forget that buying a stock is a major purchase and should be treated like one

You wouldn't buy and sell your car, your refrigerator, or your DVD player 50 times a year. 

Investing should be a long-term commitment because short-term trading means that you're playing a loser's game.

The costs really begin to add up - both the taxes, the brokerage costs, and the spread - and create an almost insurmontable hurdle to good performance. 

The amount you rack up in commissions and other expenses is money that can't compound for you next year.