Do you have sleepless nights because you are unsure whether God has forgiven your sins? Don't subject yourself to those torturous and depressing thoughts and start to LIVE, in freedom, always assured that all your sins are forgiven.
It's not as difficult as our Opponent, the Devil, wants us to think it is. Just go back to how Christ taught us to pray, and see the answer staring right back at us: "And forgive us our debts, as we also have forgiven our debtors." (Mat.6:12) Yes, the guarantee we have that our debts are forgiven, is founded in our resolve to forgive our debtors!