Below are some links to posts that provide some guidance on why and what to write in a Journal.
http://traderfeed.blogspot.com/2010/03/considerations-for-your-trading-journal.html
http://www.thekirkreport.com/2006/11/trading_journal.html
http://www.tradingacademy.com/lessons/20100302/specialtyskills_article.htm
http://www.rightline.net/education/YourTradingJournal.html
http://getrichinvesting.com/what-to-write-in-your-trading-journal/
http://www.forexexplore.com/strategies/177-strategy/1739-how-to-keep-forex-trading-journal.html
I find that it’s important to remember that sometimes there is no reason a trade was unsuccessful that can be attributed to trading decision. Sometimes prices move because of outside unpredictable news. A institutional broker can make a large move that can unexpectedly reverse or accelerate a trend. Although we look for the non-random movement of prices, random happens.