I think keeping a betting journal/diary for one is key. I did that and it opened up my eyes. I only play South African horse racing. Following my system I spotted a strange pattern. My system only works on specific tracks and with horses with certain statistics. So I only started betting on those tracks and those kinds of horses. I am a small hobbyist player, but for the first time my Interbet balance has nearly doubled in less than a month. I can't say if this trend will continue of course, but the lesson for me is to know where your strengths are and back them and don't bet where your track record is poor. Keep a betting diary and learn from it.
The following user(s) said Thank You: TheBluntPunt