You can cancel your account at any time by going to your account page and selecting the Subscriptions tab. Here you will see an option to 'Cancel' next to your current subscription.
Click the Cancel link, select the reason you wish to cancel and then confirm your cancellation and you're all done. You'll receive an email confirmation that cancellation was successful. (please note that once selecting a reason you will need to confirm you cancellation on the next page - if you don't do this your cancellation will not be processed)
Once you cancel your account you will retain access to the Academy until your current subscription period ends. You can, of course, rejoin anytime in the future!
Please cancel your account BEFORE your next payment is due and avoid leaving it to the last minute. You will retain access to the Labs until your next payment is due, so you can cancel as far in advance as you would like.