Maybe Peter thought life would be would be easy now. Jesus would take care of everything. It would be full nets from here on out. Perhaps many of us first come to faith tired and exhausted, ready to follow because our 'nets' are empty and we're about ready to give up. We are filled with hope when we meet Jesus.
We remain happy in our faith, contented with where we are. Life is good. Jesus, however, knows we need a deeper walk with him if we are to withstand the harder trials. Our desire to follow Him may be genuine, but He knows that to this point it has been an 'easy' faith. Our faith will need to be strengthened, tested, and proven.
We may not outwardly deny him to others as Peter did. But in our everyday life we can find ourselves denying Him time and devotion. - If we're not careful. We may not even think about Him until Sunday. We're busy, or tired, or sick, or... whatever. We are not following because we are not filled with His Spirit.
John 13:36 Simon Peter asked, “Lord, where are you going?” And Jesus replied, “You can’t go with me now, but you will follow me later.”
He will get our attention again. When we allow Him to fill us with His Spirit, following is no longer for our purpose but for His. That is the difference. We no longer follow because He makes our life 'better.'
We follow because He is all.