While you have capacity you can change your mind at any time. If you would like to change the content of your Advance Decision or your Advance Statement then you can easily do this by logging back into your MyDecisions account. Once you have made any changes and the new form has been signed and witnessed, you should give copies of the new form to anyone who had the old version. You should also tell them to destroy their copies of the old version.
You can cancel your Advance Decision completely by destroying it and advising anyone who has a copy to do the same.
Remember that your Advance Decision or Advance Statement will only be used if you lack capacity. So, if you still have capacity you can continue to make your own decisions.