17 or 22?

This summer I've been getting so many people telling me I look like I'm either still in high school or just got out of high school. Before that, I've never had anyone tell me that. I always thought I at least looked my age, but apparently not. It's pretty interesting, since my YOUNGER sister and I have been working at the same place these past couple of months, and every single person has thought that she is older than me. Are they saying I'm more immature than my sister?? Is it the way I dress? The way I act? The way I talk? Or just because my face is rounder? Maybe all of the above. I do get sick of people telling me how young I look, but then again I'm also getting used to it. Just wait 5 or 10 years and I will be grateful to people telling me that. In the long run, I suppose I'd rather be the one looking younger rather than older. Just gotta look at the big picture, right? See, having the right perspective and attitude changes everything.