The second principle is loss limits. Set a daily, weekly, and monthly loss limit before you start betting. When you hit the limit, stop. This is the hardest rule to follow because the gambler's fallacy tells you that the next bet will reverse the loss. It will not. The odds are the same after a loss as before. Loss limits prevent the spiral that turns a bad day into a bad month.
The third principle is record keeping. Track every bet with the date, game, line, stake, result, and closing line. Review your records weekly. If your process is sound and the CLV is positive, the results will improve over time. If your process is unsound, the records will show the pattern. Without records, you are guessing about your performance.
The fourth principle is emotional detachment. Betting should be a mathematical exercise, not an emotional one. If you are betting on your favorite team, you are not betting with an edge. You are betting with bias. If you are betting to recoup a loss, you are not betting with an edge. You are chasing. If you are betting because you are bored, you are not betting with an edge. You are entertaining yourself with money.
The final principle is knowing when to stop. If betting is no longer fun, if you are losing more than you can afford, if you are hiding your betting from people who matter to you, or if you are betting more than you intended, it is time to stop. Sports betting should be a profitable intellectual exercise for a small minority of participants. For everyone else, it is entertainment with a cost. Be honest about which category you are in.