You clicked send. Oh crap.

When you send a no-take-backs email — maybe an admission to a secret crush, or accidental reply-all — there's an instant pang of regret. It feels like there's no going back.

Meet Gmail's Undo Send feature, a lifesaving little hack buried in the Gmail Labs settings. It gives you a 10-second window to "undo" sending an outgoing email.

You just have to enable it first.

Here's how it works:

1. Click the gear icon in the top right corner of your Gmail window and select Settings from the dropdown menu.

2. Select Labs from the row of tabs.

3. Scroll all the way to the bottom where you see Undo Send and click Enable.

4. Hit Save Changes at the bottom.

5. Breathe easy.

Now when you send an email, the yellow dialogue that displays "Your message has been sent" will also give you the option to Undo.

You have 10 seconds to click on the undo button before it fades.

And objects on gmail labs are experimental and can be changed.