Strongs
metanoew metanoeo met-an-o-eh'-o
from 3326 and 3539; to think differently or afterwards, i.e. reconsider (morally, feel compunction):--repent.
Webster's 1828 Dictionary [K-Z]
repentance
REPENT'ANCE, n.
1. Sorrow for any thing done or said; the pain or grief which a person experiences in consequence of the injury or inconvenience produced by his own conduct.
2. In theology, the pain, regret or affliction which a person feels on account of his past conduct, because it exposes him to punishment. This sorrow proceeding merely from the fear of punishment, is called legal repentance, as being excited by the terrors of legal penalties, and it may exist without an amendment of life.
3. Real penitence; sorrow or deep contrition for sin, as an offense and dishonor to God, a violation of his holy law, and the basest ingratitude towards a Being of infinite benevolence. This is called evangelical repentance, and is accompanied and followed by amendment of life.
Repentance is a change of mind, or a conversion from sin to God.
Godly sorrow worketh repentance to salvation. 2Cor. 7. Matt. 3.
Repentance is the relinquishment of any practice, from conviction that it has offended God.
No one will come to Christ unless they first change their mind (repent) about sin. If the unbeliever keeps the same mindset about sin, which is he likes it, then he won't see any need for a Savior. It's only when he changes his mind (repents) and sees sin as something he wants nothing more to do with.
Repentance is simply having a change of mind towards God and away from sin, and the first step toward salvation.
It is not a work.