If you were my new TM I would think hard about how often you needed an unscheduled "personal day."
I don't have an issue with people requesting days off or swapping shifts or being sick. Not for a second. But I do often find it hard to stomach "mental health" days when the shift isn't covered. I'm not saying people don't sometimes needing them, but I think they should be requesting the time unless you are in crisis.
Without knowing your personal reasons, I would say don't do it more than once or twice a year. Obviously if you are dealing with an actual crisis (imminent death in the family, partner in a car wreck, etc.) take the time. But don't claim you need a day off because you forgot to request a day off to study for a test or catch up on homework.