While you want your mantra to be unique to you, there is no need to feel pressured to come up with some eloquent phrase or avoid one because it's been used before. What matters is you connect to it in some way, you repeat it throughout the day or during meditation, and that it helps you direct and channel your best intentions.
Just as there isn’t only one religion that uses prayer beads, there isn’t just one exact reason that a Mala has 108 beads. The number 108 has significance in many places and times throughout history. It is known that there are 108 repetitions counted with mala beads. It allows the practitioner to better focus on the vibrations and sounds of the prayers or mantras. So, why are there 108 repetitions?