​You know, you do have something to glory in.
And not like those who glory in their shame.
You have gifts, talents, accomplishments, excellencies, prizes, awards.
You have succeeded in many areas, have advanced in various fields, have had a distinguished career.
People would say you are smart, you are nice, you are a pleasure to be around.
You walk down the street, and people greet you.
All these are transient and the trifling, and nothing to glory in, compared to the glory of God in the cross.

Paul had a rich choice of things in which he could have gloried.
Amongst the Jews, he’d have been an honoured rabbi, a hero, a brilliant mind, religiously accomplished.
As a Christian he might have gloried in his sufferings, his 
relentless zeal, his tireless work for Christ.
Paul gloried in the Cross of Christ. 

​Is it easy to believe, or is it hard to believe?
It’s so hard that it’s impossible to be the whoever, the whosoever, unless,
Joh 3:5  Jesus answered, "Truly, truly, I say to you, unless one is born of water and the Spirit he cannot enter into the kingdom of God.
To see the kingdom of God, to enter the kingdom of God - something must happen to you, and that culminates in belief.

To believe is more than a moment of assent.
More than an emotional moment.
More than a moment, years ago.
In fact, it is quite plain what it is to believe.
John tells us, in chapter 1, verse 12:
Joh 1:12  But as many as received Him, to them gave He power to become the sons of God, even to them that believe on His name:
To believe, is to receive.
To not believe, is to not receive: Joh 1:11  He came to His own, and  those who were His own did not receive Him. 
John equates “believing on His name” with “receiving Him.” 
Essentially, the same.
Meaning, to take (often, literally), to get hold of.

“I believe in God” is not John 3:16.
To believe – unto salvation – is a heart transaction, it penetrates.
Rom 10:10  for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation. 
Jesus must be received to be believed.
And that is a sovereign work of God, impossible with man.