You can't! We won't let you! Only joking, if for some unfortunate reason, you wished to leave us - while we would be sad and disappointed, there would be no hard feelings!
To cancel your account, as we need this in writing if you could raise a support ticket to us via the system (go to support tab) asking us to close your account, and also give feedback as to why you wish to cancel the account (so we can see if we can help!), we can then get this sorted for you and will give you the rest of the cancellation period to take your data etc with you.