Recently, Gmail made the UNDO SEND lab feature a permanent feature in Gmail. With UNDO SEND, you can set a 5, 10, 20, or 30 second time limit to undo the sending of a message. UNDO SEND is a handy feature if you quickly realize that you have made an error or left something out in a message. If you haven't tried it, you should check it out. While UNDO SEND can allow you to stop an email and make changes or delete the entire email, it is somewhat limited.
There is a Chrome extension that will allow you to do more with your Gmail. It is called Dmail. Dmail is a simple way to send -- and unsend emails directly from your Gmail. Dmail not only allows you to set a time at which the email is destroyed, but you can also revoke the email at any time in the future. You can also send attachments, but they are NOT revocable. With Dmail, you no longer lose control of your emails after you have sent the email.
Here is the Dmail Chrome extension and the website if you want to check it out.