"Beloved, I wish above all things that thou mayest prosper and be in health, even as thy soul prospereth." (3 John 2)
God wants us to prosper more than we do.
He shared this prayer through His Beloved disciple John, the same disciple who mediated on how much Jesus loved him.
"Now there was leaning on Jesus' bosom one of his disciples, whom Jesus loved." (John 13: 23)
"Then Peter, turning about, seeth the disciple whom Jesus loved following; which also leaned on his breast at supper, and said, Lord, which is he that betrayeth thee?" (John 21: 20)
Prosperity first begins in our soul -- our will, mind, and emotions -- and this prosperity is based on walking in the truth:
"3For I rejoiced greatly, when the brethren came and testified of the truth that is in thee, even as thou walkest in the truth. 4I have no greater joy than to hear that my children walk in truth." (3 John 3-4)
What truth is John writing about?
The truth of the Gospel, which is grace:
"For the law was given by Moses, but grace and truth came by Jesus Christ." (John 1: 17)
In this verse, grace and truth are treated as one composite whole. No one can talk about truth without talking about grace, as no one can talk about being in water without being wet.
Paul also speaks about the Gospel of grace:
"I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:" (Galatians 1: 6)
"To whom we gave place by subjection, no, not for an hour; that the truth of the gospel might continue with you." (Galatians 2: 5)
Paul also wrote to the Colossians:
"For the hope which is laid up for you in heaven, whereof ye heard before in the word of the truth of the gospel" (Colossians 1: 5)
and eve to the Ephesians:
"In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise," (Ephesians 1: 13)
John also relates in his Gospel account:
"Ye sent unto John, and he bare witness unto the truth." (John 5: 33)
"And ye shall know the truth, and the truth shall make you free." (John 8: 32)
If we do not know the truth of the Grace of God, then we are not free, and thus our soul is not prospered to receive prosperity in all other things.
God delays in prospering us because He wants us to prosper on the inside, resting in the truth of the Gospel first, before anything else:
"Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: 39And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses. " (Acts 13: 38-39)
"He that spared not his own Son, but delivered him up for us all, how shall he not with him also freely give us all things?" (Romans 8: 32)
If there is a delay in your prayers answered and your prosperity delivered, grow in grace and knowledge of the Lord (2 Peter 3:18), and your delay will give way to delight.