Hello Yzen: I guess this introduction was sort-of a mixed blessing, as they say. I'm afraid enthusiasm was never my "long suit" at work either. I wonder if you could share, with your supervisor, the new perspective you've gained; or perhaps, if there is someone else in the company you feel comfortable talking with, you could ask them for some feedback with regard to how you come across & what you might do to appear more enthusiastic?

Of course, the other possibility is to simply observe other employees, see how they conduct themselves, & see if there are things they do you could adopt to make yourself appear more enthusiastic. It's unfortunate that, as someone who does excellent work, you also have to be concerned about whether or not you come across as enthusiastic. But that is the reality of the world of work if you want to get ahead.