I hate to be the bearer of bad news but "Carla Yoga" might not be a reliable source of information 😅. More generally, the advice is to never work with mantras you haven't directly received from a legitimate ācārya, who themselves has realized that mantra consciousness. The nature of mantras in this tradition is that they embody the deity in sonic form, and by working with the mantras, we achieve merging into and the capacity to see the mantric consciousness of that deity. Why one would want to recite a "personal mantra" or something of that nature is beyond me. You're already you. The point is to recognize that you're also something more than yourself, which will only become apparent after initiation and serious practice of the mantra of a deity. This is the best advice I can give on the matter and I hope it's helpful!