What happens to deleted Files?

With all governments digitally spying on each other and on its own citizens, it looks as though the best place to store sensitive info is one's own head. What happens when one hits the DEL button?

Does this make sense?
<a href="https://gizmodo.com/what-actually-happens-to-all-your-deleted-files-850015101" target="_blank" rel="nofollow noopener noreferrer">What Actually Happens to All Your Deleted Files?</a>