Hello. I mistakenly requested the deletion of my Apple ID. Is it possible to cancel my deletion request?

Apple's support document How to delete your Apple ID account has this information about how to stop an Apple ID deletion if you change your mind:

What happens if I change my mind after I have requested that my account be deleted? 

While your request is being processed, you can contact Apple Support with the unique alphanumeric access code you received, and we’ll help you cancel your request. After your account is deleted, Apple can't cancel the request, reopen your account, or restore your data.

So find the code and contact Apple immediately using the link in the text above.