Predestination troubles John Bunyan

In his book "Grace Abounding to the Chief of Sinners", John Bunyan grappled with predestination:

QUOTE
By these two temptations I was very much afflicted and disquieted; sometimes by one, and sometimes by the other of them. And first, to speak of that about my questioning my election, I found at this time, that though I was in a flame to find the way to heaven and glory, and though nothing could beat me off from this, yet this question did so offend and discourage me, that I was, especially sometimes, as if the very strength of my body also had been taken away by the force and power thereof. This scripture did also seem to me to trample upon all my desires; It is not of him that willeth, nor of him that runneth; but of God that showeth mercy (Romans 9:16).

With this scripture I could not tell what to do: for I evidently saw, unless that the great God, of His infinite grace and bounty, had voluntarily chosen me to be a vessel of mercy, though I should desire, and long, and labour until my heart did break, no good could come of it. Therefore this would stick with me, How can you tell that you are elected? And what if you should not? How then?

O Lord, thought I, what if I should not indeed? It may be you are not, said the Tempter; it may be so indeed, thought I. Why then, said Satan, you had as good leave off, and strive no farther; for if indeed, you should not be elected and chosen of God, there is no talk of your being saved; For it is not of him that willeth, nor of him that runneth; but of God that showeth mercy.

By these things I was driven to my wits' end, not knowing what to say, or how to answer these temptations: (indeed, I little thought that Satan had thus assaulted me, but that rather it was my own prudence thus to start the question): for that the elect only attained eternal life; that, I without scruple did heartily close withal; but that myself was one of them, there lay the question.

Thus therefore, for several days, I was greatly assaulted and perplexed, and was often, when I have been walking, ready to sink where I went, with faintness in my mind; but one day, after I had been so many weeks oppressed and cast down therewith as I was now quite giving up the ghost of all my hopes of ever attaining life, that sentence fell with weight upon my spirit, Look at the generations of old, and see; did ever any trust in God, and were confounded?

At which I was greatly lightened, and encouraged in my soul; for thus, at that very instant, it was expounded to me: Begin at the beginning of Genesis, and read to the end of the Revelations, and see if you can find, that there were ever any that trusted in the Lord, and were confounded. So coming home, I presently went to my Bible, to see if I could find that saying, not doubting but to find it presently; for it was so fresh, and with such strength and comfort on my spirit, that it was as if it talked with me.

Well, I looked, but I found it not; only it abode upon me: Then did I ask first this good man, and then another, if they knew where it was, but they knew no such place. At this I wondered, that such a sentence should so suddenly, and with such comfort and strength, seize, and abide upon my heart; and yet that none could find it (for I doubted not but that it was in holy scripture).

Thus I continued above a year, and could not find the place; but at last, casting my eye upon the Apocrypha books, I found it in Ecclesiasticus 2:10. This, at the first, did somewhat daunt me; but because by this time I had got more experience of the love and kindness of God, it troubled me the less, especially when I considered that though it was not in those texts that we call holy and canonical; yet forasmuch as this sentence was the sum and substance of many of the promises, it was my duty to take the comfort of it; and I bless God for that word, for it was of God to me: that word doth still at times shine before my face.

After this, that other doubt did come with strength upon me, But how if the day of grace should be past and gone? How if you have overstood the time of mercy? Now I remember that one day, as I was walking in the country, I was much in the thoughts of this, But how if the day of grace is past? And to aggravate my trouble, the Tempter presented to my mind those good people of Bedford, and suggested thus unto me, that these being converted already, they were all that God would save in those parts; and that I came too late, for these had got the blessing before I came.

Now I was in great distress, thinking in very deed that this might well be so; wherefore I went up and down, bemoaning my sad condition; counting myself far worse than a thousand fools for standing off thus long, and spending so many years in sin as I had done; still crying out, Oh! that I had turned sooner! Oh! that I had turned seven years ago! It made me also angry with myself, to think that I should have no more wit, but to trifle away my time, till my soul and heaven were lost.
UNQUOTE

Note:
For those who might be interested, this is Ecclesiasticus 2:10 in KJV:
Look at the generations of old, and see; did ever any trust in the Lord, and was confounded? or did any abide in his fear, and was forsaken? or whom did he ever despise, that called upon him?