I know from personal experience that when you mess up, whether it is small and private or big and public, Satan will try to use it against you for years. Here is the truth...
1. God has grace enough to cover your sin.
You forgave the iniquity of your people and covered all their sins. Psalm 85:2
2. God still has plans for you.
"For I know the plans I have for you," declares the Lord, "plans to prosper you and not to harm you, plans to give you hope and a future." Jeremiah 29:11
3. What you imagine people are saying is always worse than what they are really saying.
(I don't have a verse to back this one. It is just something I have learned from personal experience.)
4. You are the child of the Most High King, NOT whatever Satan is whispering in your ear.
I will be a Father to you, And you shall be my sons and daughters, say the Lord Almighty. 2 Corinthians 6:18
Whatever you have done, God is ready and able to forgive and forget. 1 John 1:9 tell us that If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness. I especially like that last part... He will purify us. So the next time Satan is trying to get you down, don't listen. Instead you tell him that he is defeated, and God has plans for you.