Amen.
I do not disagree that we must decrease our in our will and increase in His will. However I do believe the context of; "He must become greater; I must become less.” (John 3:30 NIV) was in reference to John's ministry.
Up until the baptism of Jesus Christ our Lord we have John and his disciples as the last of the Old Testament Prophets and the forerunner (as all Kings have forerunners to announce Their coming) to Jesus Christ.
John and Jesus overlap in this transition as John, the last of the Old Testament prophets, representing the Old Testament and Jesus the New. And here comes the transition, verse 30 John says, "He must become greater; I must become less." John representing the Old Testament to fade as Lord Jesus moves in full view of all.
John was a prophet who had a ministry and disciples. John didn't want them following him anymore and this transition becomes evident again;
The next day John was there again with two of his disciples. When he saw Jesus passing by, he said, “Look, the Lamb of God!” When the two disciples heard him say this, they followed Jesus. (John 1:35-37 NIV)
John is telling his disciples, look over there, that is the One I've been telling you about, there He is over there , what are you standing around me for...
Every time I read that I think there's nothing I wouldn't give to have been there.
Anyway I'm here and there are a number of other examples. Not trying to start anything I just believe the context of that verse is pivotal and has greater Biblical historical significance.