ANSWER:

You may not be able to stop them as Satan is trying to pull your legs into falling again in such sins!
Keep on fighting till your last breath and Allah will protect you.

Although I make daily tawbah and istighfar I am haunted by my past sins and I get constant flashbacks of the way I used to be and the evil I committed in my past. I am afraid my tawbah isn’t sincere enough and that I won’t be forgiven because there’s no guarantee. What can I do about this? How can I get the flashbacks to stop?