When an insurmountable obstacle stands in your way, you have no choice, other than an obvious negative choice.
When that insurmountable obstacle is removed you now have a choice, a positive one.
That "insurmountable obstacle" is man's moral inability for all in Adam. They cannot not sin.
Quickening by God replaces that "heart," metaphorically the seat of one's will, with a new "heart."
Thus, once so instantaneously quickened by the power of the Holy Spirit, the man will not not want to choose aright.
Man is doing the choosing, the believing. God is not. Rather, God is restoring the nature of man wholly corrupted in the fall of Adam to one that is now morally capable of choosing for the good.
It is futile to repeat this to those that deny the extent of the fall of Adam. Those that assume there remains in all fallen men some "seed" of righteousness, such that they are morally able to choose wisely, are assuming something unique exists within themselves that distinguishes them from their neighbors who chose badly. They are in effect adding to the efficacious grace God extends to His children, a super-added grace, contrary to Scripture. Thus, despite their lachrymose or strident claims they do not merit anything by their wise choice, the facts stand against them.
If all in Adam are equally granted the same "seed" of grace—a level playing field—permitting one to choose wisely or unwisely, then those that choose wisely need examine themselves more carefully in hopes of determining what was it in and of themselves that led them to the right choice. It is a fool's errand, for no answer by those that believe this "in Adam, yet not totally corrupt" view will escape the proper charge that they themselves have contributed to their newfound state of re-birth.
The only answer to the plain question: "Why you and not your neighbor?" is
"God did it, all of it. I did not want it. I hated God and certainly did not see any choice other than to continue in my hatred. Yet, for reasons known only to Him and not based upon anything meritorious foreseen in me, God changed my nature such that I then genuinely wanted to believe and could not do other than believe. Thanks be to God!"
AMR