Employee struggles with excessive duties

DEAR HARRIETTE: I’ve been feeling overwhelmed at work. I was hired as support for one team but have now been expected to regularly cover two large teams. I sometimes find myself struggling to efficiently and seamlessly complete tasks for my main team while juggling tasks on both ends. Per my year-end review, I think my manager noticed a shift in my attitude in the office and with my colleagues (specifically, that I’ve been less social and much more uptight). As a result, my manager let me know that if I would prefer to support only the team I was originally hired for, I just need to let them know, and they’ll begin looking for another hire.