First impression matter

I learn recently that Mozilla was not sure to hire me after my in-person series of interviews. They thought I had no personality. It's funny. I don't remember why they could have had this impression, but they know now that I do not lack personality. Maybe I was sick. Maybe it was the time zone change (but... only three hours). Maybe I was stressed out (not usual for me). Maybe it's because it was in English. No matter the reason, my first impression was not the one I usually give, and it failed me. The story had a happy ending as I got the job. As far as I don't care about what people think about me (it does not mean I don't like when people think good things about my very own self), it could have cost me this job.

What is the first impression you are giving? Think about it...