Hi janmes - Definitely, keep a log. Although I have been trading for years I only recently started a log which I can actually maintain - looking back over itrs first month I found I had been buying shares and holding longs in a falling market and opening shorts in a rising market. Not rocket science I admit but without a cool look at what I had been doing I might have not seen the significance. I also found that in one period, though I had made a profit, all this profit was entirely down to position size, not choice of direction, market or strategy - this was a real eye-opener.
I expect the log will in the future help me identify market phases when particular strategies will not work 100% and ned to be suspended or amended.