“Are my mixes too bright because my high end is overdamped?”

“Are my mixes too bright because my high end is overdamped?” Have you been in this situation: You are mixing in your room, maybe with some basic treatment, and whenever you take your mixes outside of the studio, they turn out a little bit harsh, just a bit too bright? There's just a little bit too much high end in your mixes. Consistently with every other mix, you're just obviously boosting the high end too much. And because you're also feeling that your room is overdamped you're wondering if...