Most people who wager on horse races never pick enough winners to show a profit over an extended period of time. The difficulty stems from the fact that, when it comes to wagering on horse races, they do not know their own strengths and weaknesses. The owner of a successful business, where the difference between profit and loss can be attributed to his strength for decision making (i.e., whether to stock or not stock a particular item), can be found making ridiculous wagers at the track with no regard for the effects they have on his bankroll. He has found his strengths for business making decisions, but has failed to find them when it comes to betting on horse races.
Setting up guidelines for when to bet and when to ignore a race can certainly help, but most people who set up such guidelines treat them as hard and fast rules that can never be broken. This can often result in betting on a horse when your gut instinct tells you you should pass the race, or, not betting on a horse because its odds have dipped below the 7/1 minimum you set for wagering even though you can sense a seven-length victory is imminent. (I am sure that, if I were to check my books for the past six months, I would find at least one wager I placed at odds of 6/1, despite the minimum odds guidelines I instituted last year.)
The ability to pass races when the potential for profit does not exist is what truly separates successful handicappers from gamblers. Hopefully, you will choose races that offer you profit potential, and ignore races where such possibilities are not likely. Adhering to old beliefs about betting on horses that look good on paper, when you should be finding the best bet in a race is certain to be your downfall.