Over the last couple of days I have been working with a young man struggling with his faith, specifically, his assurance of salvation. And then today, I ran across this meditation in a devotional my bride gave me in 2002.
The New Birth–Unexplainable
“Therefore if any man be in Christ, he is a new creature,
old things passed awasy, behold, all things have become new.”
2 Corinthians 5:17
“I insist that the new birth was provided in the love and grace and wisdom of God in order to draw a sharp line between those who acquire Christianity by any other method and those who have experienced regenesis . . .
[S]ome professing Christians are still trying to find natural and reasonable explanatons for that which God has said he would do miraculoursly by His Spirit.
Let me warn you that if you are a Christian believer and you have found a psychologist who can explain to you exactly what happened to you in the matter of your faith, you have been unfrocked! . . . The honest psychologist can only stand off respectully and say, ‘Behold the works of the Lord.’
He never can explain it! 
The humblest Christian is called to live a miracle, a life that is a moral and spiritual life with such intensity and such purity that no human being can do–only Jesus Christ can do. 
[T]he . . . genuine child of God is someone who cannot be explained by human reasoning. 
 I Call it Heresy, pages 035-036.
 The Tozer Pulpit Volume 2, page 060.
 The Tozer Pulpit Volume 3, page 047
- All quotes and references are from Tozer on the Holy Spirit: a 366-Day Devotional, compliled by Marilynne E. Foster