It is impossible to disappoint others because you don’t disappoint them, their expectations of you disappoint them. You are not responsible for their expectations of you.
It is impossible to disappoint yourself because you can only disappoint your expectations of yourself and you are not your expectations. You are responsible for your expectations of yourself.
However, you can fail to fulfill your responsibilities. In this case, you will violate your boundaries, and you cannot expect someone to save you from the consequences of your actions, because this is what you need to experience in order to grow.