I'm also generally running late. Like I'll get places on time, but just barely. If I'm anxious, I do dumb stuff, like today, when I decided to detangle a necklace so I could wear it, but I could have just skipped a necklace or worn a different one. But in reality, I was nervous about my marriage counseling appointment, so I was subconsciously finding ways to procrastinate. I'm generally just bad at time management overall. I also hate being too early for stuff, because then I just have to sit there and wait.

But for OP, I'm not sure what being late to an appointment would accomplish. Especially because T told you to be late. So...if she told you to arrive 10 minutes late, it's almost like that would be arriving on time! If there are other areas where you have perfectionist issues (I have some of that too), maybe you could focus on those instead?