You are at the store buying something and the clerk gives you $10 too much change. You keep it. After all, it was his mistake and not yours. You go into the toy store next door and buy some new handle grips for your bike.
You know the money wasn't yours. You start to worry that the clerk will have to pay the store $10 out of his wages. Whenever you ride your bike, the new handle grips remind you that you were dishonest.
When the clerk gives you the $10 change, you tell him he has given you too much and give the $10 back to him. He says thanks, but as you walk out, you start thinking about the new handle grips you could have bought with the $10.
You feel good and strong inside because you were honest. Whenever you ride your bike, you remember that you need handle grips, but you also remember that you were honest.
You are sitting in class taking a really hard test that you forgot to study for. The girl across the aisle seems to know all the answers, and her paper is so easy to see. You copy a few answers and end up getting an A- on the test.
Your conscience bothers you. You know that you didn't deserve the A. You wonder if anyone saw you cheating. It's a little hard for you to get to sleep that night. On the next test you're unprepared again.
You're a little mad at yourself for not studying harder and you're really worried about your grade. Still, you keep your eyes on your paper and do your best. Unfortunately your best that day is only a C on the test.
You resolve to study harder. Next test you do better. You like yourself because you know you are honest. Other people like you because they know you can be trusted.