Luke 7:47 - “Therefore, I tell you, her many sins are forgiven - for she Loved much. But he who has been forgiven little Loves little.”
Think about it this way. Say you owe money to two different people. To one you owe five dollars; to the other you owe five hundred dollars. Now you have fallen on hard times and have been unable to pay any of it back. These men see this and they have compassion on you, so they tell you that you do not have to pay them any of the money you owe.
Now, in your situation, you were unable to satisfy either of the debts, but to which will you show more appreciation? You will have more gratitude to the one who forgave the larger debt. If both of these men were calling for help you would go to this one first because he forgave more.
Now look at your relationship with God. We have all been forgiven of all our sins. As Jesus says here, though, there are different appreciation levels for this forgiveness. ‘The one who has been forgiven much Loves much and the one who has been forgiven little Loves little.’
In reality we must realize that all sin is equal and all sin deserves death, so we all have been forgiven the same debt. But we don’t all see it this way. In our minds we see some sin as not being as bad as other sin. We think that the little ‘white’ lie we told isn't as bad as the guy who killed someone. From the human perspective this is true, but from the eternal perspective and in God’s eyes these are equal. Both deserve death; but both will be forgiven if you come to Him.
So when Jesus is speaking to His disciples here, why is He talking about different levels of Love? It is because we Love to the extent we realize we have been forgiven. If you think your sin really isn't that bad, you won’t appreciate God’s forgiveness as much as the one who realizes that his sin deserved death.
We will not be able to Love God to the extent we are called to, until we realize how devastating our sin really is. When we realize how bad our sin is and how much God has truly forgiven we will actually be able to Love Him more.