just an addition: to say in both instances it's a timing and endurance issue (on our part). Even in the case of the Lord saying "thy sins are forgiven" it's still conditional on our "sinning no more."

Repentance never truly ends. When you turn from the sin, you can't turn back again without voiding your forgiveness (much like Lot's wife). Hence the scriptural emphasis on enduring to the end.

However, I will say there is beauty and power in the Atonement in the fact that we can repent, and repent again. There-in lies the true mercy of the Atonement... we get more chances than we likely deserve, and I am eternally grateful for it.