When a person realizes that a particular action,
or a certain line of conduct, or perhaps the whole
direction of his life, has been wrong, and honestly
resolves to change his conduct, he has repented.
The Bible makes true repentance an essential
condition for any spiritual progress, and for the
forgiveness of sin. Jesus said, "Except ye repent,
ye shall all likewise perish." (Luke 13:3)

Repentance does not mean grieving for past
mistakes, because this is dwelling in the past,
and our duty is dwell in the present and make
this moment right. Worrying over past mistakes
is remorse, and remorse is a sin, for it is a refusal
to accept God's forgiveness.

Emmet Fox (1886-1951)
Irish spiritual leader, instrumental in the
founding of Alcoholics Anonymous
From "Around the Year With Emmet Fox