Here is a excerpt from John Bunyans book "Grace abounding"

Upon a time I was somewhat inclining to a consumption, wherewith, about the spring, I was suddenly and violently seized with much weakness in my outward man, insomuch that I thought I could not live. Now began I afresh to give myself up to a serious examination after my state and condition for the future, and of my evidences for that blessed world to come; for it hath, I bless the name of God, been my usual course, as always, so especially in the day of affliction, to endeavor to keep my interest in the life to come clear before my eye.

But I had no sooner began to recall to mind my former experience of the goodness of God to my soul, but there came flocking into my mind an innumerable company of my sins and transgressions, amongst which these were at this time most to my affliction, namely, my deadness, dulness, and coldness in holy duties; my wanderings of heart, of my wearisomeness in all good things, my want of love to God, His ways, and people, with this at the end of all, Are these the fruits of Christianity? are these the tokens of a blessed man?

At the apprehension of these things my sickness was doubled upon me, for now was I sick in my inward man, my soul was clogged with guilt; now also was my former experience of God's goodness to me quite taken out of my mind, and hid as if it had never been, nor seen. Now was my soul greatly pinched between these two considerations. Live I must not, Die I dare not; now I sunk and fell in my spirit; and was giving up all for lost; but as I was walking up and down in the house, as a man in a most woeful state, that word of God took hold of my heart, Ye are 'justified freely by his grace, through the redemption that is in Christ Jesus' (Rom. 3.24). But oh, what a turn it made upon me!

Now was I as one awakened out of some troublesome sleep and dream, and listening to this heavenly sentence, I was as if I had heard it thus expounded to me: Sinner, thou thinkest that because of thy sins and infirmities I cannot save thy soul, but behold My Son is by Me, and upon Him I look, and not on thee, and will deal with thee according as I am pleased with Him. At this I was greatly lightened in my mind, and made to understand that God could justify a sinner at any time; it was but His looking upon Christ, and imputing of His benefits to us, and the work was forthwith done.

And as I was thus in a muse, that scripture also came with great power upon my spirit, 'Not by works of righteousness which we have done, but according to his mercy he saved us,' etc. (Tit. 3.5; II Tim. 1.9). Now was I got on high; I saw myself within the arms of grace and mercy; and though I was before afraid to think of a dying hour, yet now I cried, Let me die. Now death was lovely and beautiful in my sight; for I saw we shall never live indeed till we be gone to the other world. Oh, methought this life is but a slumber in comparison of that above; at this time also I saw more in those words, 'Heirs of God' (Rom. 8.17), than ever I shall be able to express while I live in this world. 'Heirs of God'! God Himself is the portion of the saints. This I saw and wondered at, but cannot tell you what I saw.