Yes, if you decide that you need to cancel or revise your pledge you can do so as long as the campaign is still live. Once a campaign ends, it is no longer possible to make any changes or cancellations.
To cancel a pledge you'll need to log in (or create an account if you pledged as a guest) with the email address you used when you made your initial pledge.
Once you've logged in you can cancel or edit your pending pledges by clicking here. You'll just want to select the Manage button that looks like this:
