When asked if a person is nice we often think of the nicest thing the person has ever done. Nothing can be further from the truth. The best way to see if how nice a person is, is to see how "un-nice" he can be in a given situation.
While working in the post office yesterday a man came in to submit his passport application. The man was with his 4-year old son. We made some small talk about his son and he seemed like a really nice person. That is, until he found out that he was given the wrong information about how his form should have been printed out. Apparently he had taken a couple of hours off work to come into the post office. I was not attending to him, but I heard him slam something on the counter. He ranted about how much it cost him to come in, only to find that he had wasted his trip. He wanted the name of the person who gave him the information the day before and he threatened to complain to the postal authority. He was a different person from when he first came in.
We often think the best of a person's character when we first get to know the person. It is only after knowing the person for a long time that we begin to see his real strength and weaknesses. I am not saying this is a bad thing to do. All I am saying is that if you are going to strike a long term relationship with a person, you don't really know what he is like until you have seen the worst of him, or how "un-nice" he really can be.