The Great Exchange is between the Creator of the universe, and who-so-ever-will. Immanuel brought Grace and Truth with Him; and He made them available for all - that are Willing. The "heart" is deceitful, and desperately wicked: who can know it[Jer.17:9]? GOD knows it!
Grace and Truth were not new: it was pronounced in Ex.34:6,7 - but this was for the House = the 12 Tribes of Jacob [Gen.35:23-26], only. Immanuel open this blessing up to the entire globe: on one condition - will for WILL!!!
Will = pleasure, delight, goodwill, acceptance, desire, etc.. What one wishes or has determined shall be done. Of the purpose of GOD to bless mankind through Christ Jesus. Of what GOD wishes to be done by us. Choice.
We all must be born from above: born of woman into time. Purpose is for us to voluntarily decide which Father, and Will to follow. It is GOD's Will that all would come to the realization of Christ Jesus - and do, His Will.
Our prayer; "not my will, but Thy Will." "Thy Will be done, on earth, as it is in Heaven." "Doeth the Will of my Father shall enter the Kingdom." We should know his Will and approve the things that are more excellent[Rom2:18]. Intercession for the saints, according to the Will of GOD[Rom.8:27].
Impossible with man: possible with the LORD.
We must Exchange our will, for HIS - perfect Will.