Part of you is aware that what you think you want is not always good for you. How do you choose when to detach from certain desires? When is something potentially destructive behaviour?
1) Foresee results before you act. If you are on a diet, and you truly hope to lose weight, then that yen for a whole chocolate cake does not serve you. It is important to connect how certain behaviours will undermine your desired results so you can learn to discipline your mind differently.
2) Examine the giving-up process. If you are working to give up an addiction and your mind tells you to feed your habit, then you could fall into a trap. The reasons which prompted you to start doing something unhealthy offer insight into the imagined pain of stopping. People rarely resist change for reasons they assume. Delve deeper to get answers.
3) Look for patterns. If you think you want a relationship with a certain person, but it is not working, and the scenario reminds you of a past relationship, then it is possible you are not consciously aware of a pattern. Repeated experience of something not working the way you want can create tendency to cling to people who are not good for you. Time to wake up.
4) Listen to your feelings. If you are asked to do something dishonest in exchange for getting what you think you want, then the means to the end could undermine the goal. Your feelings are a dependable gauge. What feels good, works. Anything else does not. Learn to discern the real difference.