Investors have myriad reasons for buying and selling securities, but unless you can remember each one you’ll never learn which decisions led to a profit. A trading journal can help.
A journal forces you to explain the reasoning behind each investing decision you make, adding logic and diligence to your investing process. After a while you’ll be able to spot which decisions resulted in a profit, and which ones cost you money.
Many investment bloggers (Canadian Capitalist included) began their blogging careers this way. Investing ideas, lessons and experience are all freely available online, but the best lessons are through trial and error.