The promise of Amendment is an essential part of Penance. It is a necessary element in all true contrition. Thus, the penitent promises "true amendment" before he receives Absolution. If he allowed a priest to give him Absolution without firmly purposing to amend, he would not only invalidate the Absolution, but would commit an additional sin. The promise to amend may, like any other promise, be made and broken; but the deliberate purpose must be there.
No better description of true repentance can be found than in Tennyson's "Guinevere":—
For what is true repentance but in thought—
Not ev'n in inmost thought to think again
The sins that made the past so pleasant to us.
Such has been the teaching of the Catholic Church always, everywhere, and at all times: such is the teaching of the Church of England, as part of that Church, and as authoritatively laid down in the Book of Common Prayer.
God alone can forgive sins. Absolution is the conveyance of God's pardon to the penitent sinner by God's ordained Minister, through the ordained Ministry of Reconciliation.
Lamb of God, the world's transgression
Thou alone canst take away;
Hear! oh! hear our heart's confession,
And Thy pardoning grace convey.
Thine availing intercession
We but echo when we pray.