Key to being the Hero is that it is a commitment the character keeps because he willingly wants to. There are no talismans or fail-safes preventing the breaking of the vow, nor are they needed — the character's willpower and resolve are the only requirements.
Note that the Heroic Vow doesn't necessarily have to be spoken (or written); a hero's behavior enforced with sheer personal willpower counts. If the vow is spoken/written, it may become a Badass Creed.
Some Heroic Vows are so commonplace, they have their own tropes:
- Celibate Hero (will not have romantic or sexual relationships)
- Doesn't Like Guns (will not use firearms)
- Never Hurt an Innocent
- Thou Shalt Not Kill (will not commit murder — sometimes won't kill anything)
- Wouldn't Hurt a Child
- Wouldn't Hit a Girl
- Not using a Dangerous Forbidden Technique is frequently requested by a Mentor or Morality Chain, or self imposed after seeing the potential consequences.