When to use it
Use it when you can't meet a deadline and want to ask for more time. Ask for a specific extra amount of time, give a reason tied to quality, and propose the new date. That's easy to approve. Putting yourself down doesn't help anyone.
Example
You: “I need two more days to do this well. Can I send it Wednesday instead?”
Manager: “Wednesday is fine.”
In an email or Slack message
By email: “I need two more days to finish the analysis properly. Could I send it Wednesday instead of Monday? If Monday is firm, I can send a partial version then.” A fallback makes it easier to approve.