John Bunyan wrote of his struggles with Hebrews 6 in Grace abounding to the Chief of Sinners, here's a clip from it;
When I had with much deliberation considered of this matter, and could not but conclude that the Lord had comforted me, and that too after this my wicked sin: then methought I durst venture to come nigh unto those most fearful and terrible scriptures, with which all this while I had been so greatly affrighted, and on which indeed, before I durst scarce cast mine eye (yea, had much ado an hundred times, to forbear wishing them out of the Bible), for I thought they would destroy me; but now, I say, I began to take some measure of encouragement, to come close to them to read them, and consider them, and to weigh their scope and tendency.
The which when I began to do, I found their visage changed: for they looked not so grimly, as before I thought they did: and first I came to the sixth of the Hebrews, yet trembling for fear it should strike me; which when I had considered, I found that the falling there intended, was a falling quite away; that is as I conceived, a falling from and absolute denying of the gospel, of remission of sins by Jesus Christ; for, from them the apostle begins his argument, verses 1, 2, 3, 4. Secondly, I found that this falling away, must be openly, even in the view of the world, even so as to put Christ to an open shame. Thirdly, I found those he there intended, were for ever shut up of God, both in blindness, hardness, and impenitency: It is impossible they should be renewed again unto repentance. By all these particulars, I found to God’s everlasting praise, my sin was not the sin in this place intended.
First, I confessed I was fallen, but not fallen away; that is, from the profession of faith in Jesus unto eternal life.
Secondly, I confessed that I had put Jesus Christ to shame by my sin, but not to open shame; I did not deny Him before men, nor condemn Him as a fruitless One before the world.
Thirdly, Nor did I find that God had shut me up, or denied me to come (though I found it hard work indeed to come) to Him by sorrow and repentance: blessed be God for unsearchable grace!