The bottom line is that you shouldn't worry about feeling guilty at all, because God already paid that price for you. Check out this blog post by Karen Hancock:
Guilt, according to the American Heritage dictionary is
Remorseful awareness of having done something wrong.
Self-reproach for supposed inadequacy or wrongdoing.
It’s a sin because it’s adding to the work of our Lord on the cross. If He took all the punishment for all our sins — and He did — then why would we feel we need to punish ourselves?
1 Jn 1:9 says, “If we confess, [name, cite] our sin, He is faithful and just to forgive us our sin and to cleanse us from all unrighteousness.
Jeremiah 3:13 says, “Only acknowledge your iniquity, that you have transgressed against the LORD your God…”
Acknowledging that you have sinned carries no merit. You’re just agreeing with God that what you’ve done/said/thought is a sin, and at that point He forgives you the sin and cleanses you from all unrighteousness. The cleansed vessel of the soul is then suitable to be filled or controlled by God the Holy Spirit and fellowship is restored.
The rest at:
Guilt is a Sin « Writing from the Edge 2
But to answer your question specifically: Who knows. The Devil will indeed accuse you, but sometimes we're our own worst accuser. But it's something you shouldn't let get to you, and feeling guilty and down on yourself is quite natural. You just need to remind yourself that it doesn't matter. God knew you would do that sin even before you were born. Yet, He has forgiven you, and always will forgive those who call out to Him. If you weren't saved, you wouldn't be struggling with any kind of guilt to begin with. When it comes, remind yourself of what Christ did for you. Just pick yourself up and keep on living.