Edwards on Calvinism

I've been reading a biography of Jonathan Edwards, and was very interested to find out his change of belief regarding the doctrines of predestination and election as he grew spiritually. Quoting from Ian Murray's biography, which is quoting Edwards' Personal Narrative:

"From my childhood up, my mind had been full of objections against the doctrine
of God's sovereignty in choosing whom he would to eternal life, and
rejecting whom he pleased; leaving them eternally to perish, and be
everlastingly tormented in hell. It used to appear like a horrible doctrine
to me,"

and later, after coming to a new conviction on the subject:

"But I have often, since that first conviction, had quite another kind of sense of God's sovereignty than I had then. I have often since had not only a conviction, but a delightful conviction...Absolute sovereignty is what I love to ascribe to God. But my first conviction was not so."

So what produced this change? It is what Ian Murray describes as the "Valley of Humiliation" in Edwards' life. Quoting again from Murray:

"He learned by experience, as others had done before him, that while those who have little awareness of the real nature of sin may assert man's ability to repent and believe, . . . those who know the true condition of human nature (italics mine) can find comfort only in the knowledge that God saves by his sovereign good pleasure adn for the praise of the glory of his grace. . . Men must be saved by sovereign mercy or not at all."