“[Repentance] is not a transient action, as Papists and some ignorant creatures imagine, as if a sigh for sin, an act of sorrow for it, a confession of it with a ‘God be merciful to me a sinner,’ were repentance.  No, no; these may be acts of repentance while they proceed from a truly penitent heart.  But repentance itself is not a passing act, but an abiding grace (Zech. 12:10); a continuing frame and disposition of the soul; a principle lying deep in the heart, disposing a man to mourn for and turn from sin on all occasions.

It is not the passing work of the first days of one’s religion, as some professors take it to be; but a grace in the heart, setting one to an answerable working all the days of his life.  It is a spring of waters of sorrow in the heart for sin, which will spring up there while sin is here, though sometimes through hardness of heart it may be stopped for a while.

They that look on repentance as the first stage in the way to heaven, and looking back to the sorrowful hours which they had when the Lord first began to deal with them, reckon that they have passed the first stage, are in a dangerous conditionAnd whoever endeavours not to carry on their repentance, I doubt if they ever at all repented yet. As when Moses had smote the rock in the wilderness, and the waters began to gush out, those waters ran and followed them in the wilderness: so the heart first smitten with repentance for sin at the soul’s first conversion to god, the wound still bleeds, and is never bound up to bleed no more, until the band of glory be put about it in heaven (Rev. 21:4).

Hence initial and progressive repentance, though the former be the repentance of a sinner, the latter of a saint, are no more different kinds of repentance, than the soul’s virgin love to Christ, and their love to him through the course of their spiritual marriage with him; or than faith in the first, and after actings.  But as the midday and evening sun are the same with the morning sun, so are these; though the rising morning sun may be most noticed by the traveler, who having traveled in the night, was thereby brought from darkness to light.”

– Thomas Boston, Repentance: Turning from Sin to God – What It Means and Why It’s Necessary, 31-32 (emphasis mine).