Although we are encouraged to be humble, this is only when we are doing good deeds. This means that even when we think we have done much good, we must always remember that no man has yet fulfilled his obligations fully to G-d. However, when we go out into the street and are faced with tests, we need to turn on our haughtiness module. For this is what the attribute of haughtiness was created for, as it is stated (about one of the ancient Jewish kings) "Vayigbah Libo Bidarkei Hashem" - "and his heart was aloof in the ways of G-d". In other words, we have to realize how great each and every one of us is. With every deed we do we can shake all the upper worlds, for good and for bad. Each and everyone of us was created in the image of G-d. With one mistake, one moment of weakness, we can be cut off from the source of life itself, forever. And should you ask, "can one mistake really cut me off forever"? Well, think about it. You're driving down a two way highway and a big truck is coming towards you on the other lane. Your not in imminent danger as long as you stay on your lane, but one twist of the steering wheel in the wrong direction and it's all over. So take your choices in life seriously. Hold on to G-d and choose life!