The fact is it is easy to say but it is really difficult to act, specially when you are participating in the social aspect of your life. From my short existence I have already seen humble leaders. I enjoy being in a soccer team where the more experience players help those who are just starting. For example if they make a bad pass, instead of them shouting at the less experience players, they are encouraging them to keep on playing and telling them how to improve. I mean they can get angry at you for a while because you are not focusing on the game but at the end they will always say something that will make you feel better.
Another clear example is when you are hanging out with a group of people. There will always be that person who won't talk you you simply because you are not worth talking to. Or even worse, the person that only opens his mouth to say something negative about someone because that will make him feel better.
No one is perfect i this life, everybody makes errors. Reflecting back, there have been a lot of times where I haven't show humbleness and acted if as I where superior. Being humble is not something that you will convert from one day to the other. It requires a new attitude and a new way to see the world.