What does John 3:28 mean?

In verse 26, John the Baptist is told that Jesus is attracting a greater number of followers. In verse 27, he responds by saying that God is ultimately in control. Here, in verse 28, he reminds everyone that this shouldn't be a problem. The Baptist made it very clear that he was not the Promised One (John 1:20). He was simply preaching in order to prepare a path for the Messiah (John 1:23). In fact, the Baptist went out of his way to say that the One who is coming would be far better, and far more worthy, than he was (John 1:27).

Later, John the Baptist points out Jesus (John 1:29). He specifically says that this man is the One who is coming. The Baptist even tells some of his students to leave, and follow Jesus (John 1:36–37). There is no reason for anyone to think that Jesus' success will make the Baptist jealous. If anything, it's proof that what the Baptist preached was true, and that his mission was a success! John compares himself to a best man at a wedding, happy for the groom, in verse 29.