Boss says “your work is good but why your face is like this like you’re not enjoying the work.”

Needed a leave for birthday so I knew they're going to say something because one of their most important employee will not be there. This was their “feedback” to me before I take few days leave. I'm giving them 12+ hours a day and they don't have any complaint about the actual work but yeah have to say something to me just because I won't be there for few days.