How do you know when a person is trying to convince themselves that the individual they are with is a good person?

It's called "making excuses" for that person. If the person is grouchy, bad mannered, swears around you, isn't respectful of you and you make excuses such as "Oh well, he/she could just be having a bad day" to "he/she really loves me and just sounds off like this around me because he/she loves and trusts me" are excuses! The guy has NO respect for you. Dare to be your own person and expect respect and having ANYONE in your life treat you as well as you treat them. These are signs of a person that doesn't have your best interests at heart: If the person makes dates and never shows up and then lies about it; If they are disrespectful of your family and friends. If they constantly swear around you and say little else. If they ignore what you have to say. If they make love to you and simply walk out the door without as much as a goodbye. If they flirt with the opposite sex or cheat. These are a but a few signs. The rule of thumb I lead my life by is, "if I treat others with respect and they don't treat me the same way I at least let them know how I feel and if they don't clean up their act then I kick them to the curb." Sometimes it really hurts my heart, but many times it's refreshing!