We all would like to be popular to one degree or another. We would like to have people pay attention to us. How we behave when we get what we want can say a lot about our character. What can tell more though is how we handle competition.
John the Baptist was one of the most famous figures of his day. He had a big following. But one day it became clear that his prominence was being eclipsed by another; Jesus of Nazareth. Many people would have become jealous. Many would have decided to oppose Jesus. Not John though. He simply said: "He must become greater; I must become less."
There's a lot packed into that.
One thing that strikes me is that here is no causal relationship. John is not saying that Jesus' becoming greater depends on John's becoming less, as though John's voluntary capitulation was required for Jesus' greatness to grow. John is simply stating the fact that as Jesus becomes greater, he, John, will become less.
There is no hint of regret or anger in that admission of inevitability either. John accepts this as the end result of his ministry. He accepts this as being the fulfillment of all his work. So why then should he be upset? He has done all that he wanted, all that he was born to do.
If I may speculate for a moment: John had something that we typically lack; a sense of destiny. He had a strong sense, a specific sense of why he was alive. He knew specifically what his ministry was about, and when it was finished, when it had accomplished its goal.
The fact that John did not live long afterwards probably didn't bother him; he had done the greatest thing any of us can; fulfill life's purpose. Why would we want to live long after that?