In John 3:30, John said to his disciples:
"He must become greater; I must become less."
Ever since John was in the womb he knew Jesus as Lord. (Luke 1)
Later, while baptizing people, he said he wasn't even worthy to untie Jesus' sandals. (Luke 3:26)
John's whole life he knew his job, his purpose. He was sent ahead of the Christ. (John 3:28)
Like John said, Jesus must become greater; I must become less!