All by (one's) lonesome American British informal
Used to refer to someone who is entirely alone, without anyone else.
I'm sitting on the balcony all by my lonesome.
Jack has lunch all by his lonesome at the cantina after breaking up with his girlfriend.
My roommate returned to his hometown, so I have been at the dorm all by my lonesome for 2 months.
Used to say someone is alone
Without help or support from others
Be on one's own.
Isolated, lonely, or abandoned
To live alone as a bachelor