At work you're one person. At home, another. At the family party, a third person who has to explain your job to five aunties who still think you 'do computers'.
Switching between worlds all day takes real energy. Being tired isn't a personal failing, it's your nervous system doing overtime.
Give yourself a buffer: ten minutes in the car or on the bus between worlds. Music on, shoulders down, jaw unclenched. You don't have to be everyone at once.