“And the child grew, and waxed strong in spirit, and was in the deserts till the day of his shewing unto Israel.”
Luke 1:80

We are given a peak into John’s discipline concerning his purpose— he knew who he was and who he was not, he knew what he was sent to do and what he was not sent to do:
“And he confessed, and denied not; but confessed, I am not the Christ. And they asked him, What then?.. He said, I am the voice of one crying in the wilderness, Make straight the way of the Lord, as said the prophet Esaias.” John 1:20-23
The period of preparation is a period of precision, where it becomes clear that probably God wouldn’t have you being everywhere, doing everything but there’s a specific reason for your being here.
The Bible tells us of Jesus, after he went to pray up the mount of transfiguration, it became clear to him where he ought to be and what he was to do there:
“They also looked bright and glorious. They were talking with Jesus about his death that would happen in Jerusalem.” Luke 9:31, ERV
One visible expression after the period of preparation is precision of purpose and direction accordingly.

Bible Reading Plan: Jeremiah 13 and Genesis 17