You can cancel your Pro subscription at any time from your Plan page. Click the 'Manage Your Subscription' button to open your plan settings.
After you cancel you'll have access to Pro features until the end of your current billing period.
During the cancellation process you will be asked for a reason for cancelling. I value any feedback you can give at this point. Whatever your reason for cancelling, please let me know.
Note that if you cancel then resubscribe you'll pay the current cost at the time you resubscribe.