I am Cory.
I am sorry you have sent an email by mistake that you want to recall.
Unfortunately there is not a way to recall the email you have just sent.
Sending an email is kind of like mailing a first class letter at the post office. There is not a way to stop the process once you mail it.
However, Gmail does have a feature that you can use for future messages.
It is called Undo Send.
If you login your account and click https://mail.google.com/mail/?shva=1#settings/labs to go to the labs section.
Scroll down to Undo Send and choose Enable then click on Save Changes.
Next time you send an email you will see a meesage at the top to undo/cancel.
I believe it lasts about 20-30 seconds after you send the message.
If you have any questions please reply and i will be happy to assist you further.
Have a delightful day!