I'm sure it has happened to everyone out there; you have just clicked on the send button for an email, then you realize that your future life is ruined as a result of that email, and then you dream of time travel. Now with the latest Gmail labs feature, Undo Send, you can go back in time and stop that nasty email from being sent...not quite. What happens is that the email will be placed "on hold" for 5 seconds. This will give you time to simply click on the undo button, and save your future life. I just gave it a try, it was super easy to setup, super simple to use, and I think a super addition to the Gmail labs warehouse.