They are made to keep you disciplined and away from trouble.
You should come up with your own rules and set of expectations for when you trade.

Rules apply more toward internal psychology than stock trading in general.

Examples of Trading Rules

1. Do not force a trade: Many times traders and stock brokers become bored and try to make trades even if there aren't trades available If you don't see an opportunity, do not trade. Spend the day doing something else.

2. Take profits: Whether you are trading daily, monthly, swing trading, etc do not forget to take profits. The stock market goes in cycles so you need to make sure you're taking profits because eventually the stock will start retracting.

3. Be patient: If a stock is going up, let it run its course. If a stock is going down, be patient and wait until it hits the bottom. Even if the stock is retracting slightly, be patient.

4. Always honor stops: For example, if you bought a stock for $50 and you have a $1 stop, and the stock dips down to $48, you should get rid of the stock and take a small loss rather than waiting for it to continue to descend. The same goes for making profits.

5. Never trade earnings plays: Even if the earnings are great, the stock might tank. It's all a matter of the buyer/seller's perception. You have to keep in mind the perception of the news, rather than the news itself.

6. Always set monthly/yearly goals, not daily: Don't focus on daily fluctuations. This is why it is important to be patient. If the average of your trades are positive then you don't need to worry.

7. No trading once the day loss exceeds more than $X: This mostly applies to day trading. Decide on a figure that you're comfortable with, and do not continue to trade once your day loss exceeds that number. You don't want to keep killing your account.

8. Get in before headlines: Get in before the headlines rather than trying to play the headlines. That way you get the full potential either on the upside or the downside.

9. No tips, do your own homework: Don't give out tips and don't listen to them. If people are looking for feedback then do so in a neutral way. Do not be influenced by tips; this goes along with watching TV.

10. Shrug off losses if the rules are followed: There is always another day and there is always another trade. The market will still be there. Don't let your losses stress you out if you followed the rules because it will affect you in the future. You want to be able to trade confidently and effectively the next time.

You don't need to follow all of these rules all of the time, but they're a good starting point.