"On my own authority" refers to the decision or action made by an individual without any external approval or permission. Some synonyms for this phrase include independently, autonomously, self-reliantly, solo, alone, and without supervision. These terms reflect the concept of making a decision or taking charge of a situation without relying on others for guidance. "On my own accord," "single-handedly," and "freely" are other synonyms that express personal agency and freedom to act without external constraints. While it is important to seek advice and collaborate with others, there are times when relying on one's own authority can be necessary for achieving personal growth and success.