And it's a teaching of Jesus, from the Lord's prayer.
'Forgive us this day our debts, as we forgive our debtors'
He's reminding us that we incur debt (sins) against God because of our old (fleshly) nature.
Repentance is a daily process in the life of a christian, like washing hands. Should be as natural as breathing!
'Once saved always saved' is a screwy theology from Jesus' words about Not Loosing One of His people.
Salvation is not a warranty, it's a repentant, loving and servant-minded, intimate relationship with God. It's daily, and it's a cruel cheating of Jesus' blood to come once, and never come again.