Vows are personal. The are what you are vowing to do. Do not vow to do anything you don't think you can complete. They are serious and need to be taken seriously. Some suggestions;
I vow to do the best I can while learning the ways of magic.
I vow to do as little harm as possible to myself and others as I practice.
I vow to learn from my mistakes and make amends for the things I have done wrong.
I vow to listen to the guidance of others and make the decision that is best for me.