Leah Hayes, a casual friend, asked this question on a facebook page: "You have sinned and sinned big. You are caught in it no two ways about it. You directly disobeyed God about something you were certain He said not to do. There is no going back to undo what you have done. Now what?"
She was not actually troubled about anything, she just was curious what others might say in response. So here is my take on it.
Grace means accepting 100% of the ownership of your choices and actions. It also means accepting the fact that before God there is simply nothing you can do about it. It is what it is. The task before you now is to discover how even this is one of the things that the grace of God can cause to work together for good. Grace causes everything to turn out exactly as if it had been plan A all along even though it was not.
Grace so fully restores that it is impossible to ever know if the things that have come to pass were planned all along or if they were merely the redemptive dynamics making up all the difference. If grace did not work this way there would be no hope for any of us. Being godly means being gracious to each other.