Jesus was a physical man that people could see & follow around. Fast forward to today. We are now Christ's body, His visible & physical representation in the earth. Jesus has finished His work & ascended. Jesus has already increased & He wants us to recognize that so we may increase in Him. His love & the sharing of His divine glory cause us to increase in Him. Being loved & knowing we are loved in that way by Him is what increases the opinion & awareness of Jesus in the world. It isn't a legalistic obligation to witness or praise that does that. If we aren't praising Him for His goodness to us what are we praising Him for? If we aren't witnesses of His love what are we witnesses of? Love builds up (1 Corinthians 8:1). Love does not tear down. God is love, God builds us up.
The only people that should "decrease" today are those who "draw a following to themselves" & those who "distort the truth" (Acts 20:30). God does not want any of the rest of us to "decrease" ourselves at all. So many of us "decrease" ourselves with false humility, the refusal to value ourselves, the refusal to see ourselves as anything but "unworthy." God has increased our value & worth beyond our imaginations.
To "walk in a manner worthy of our calling" as spoken of many times in the New Testament isn't to strive to keep commands or stay away from sin. It is to "walk in a manner of worth" where you recognize the worth of yourself & others through God's eyes. Doing so will result in love & good deeds. But if you try to make yourself worthy of your calling by attempting to love & do good deeds you are spinning your wheels because God values whos more than dos. It is people that He treasures, not what people can do for Him. Of course He enjoys it when His children join in & work with Him. But our calling is to be reborn into the family of God. We are called to be sons & daughters. To say, "I want to know my daddy."
"May you let the Lord Jesus cause you to increase and abound in love for one another, and for all people, so that in this lifetime you may see with your hearts that He has made you blameless & holy in the sight of God our Father." (1 Thessalonians 3:12-13)