by oneself
Definitions
Without the help or company of others; alone.
Without assistance; independently.
Examples
She decided to travel across the country all by herself.
He learned how to play the guitar by himself using online tutorials.
The child was proud to tie his shoelaces by himself for the first time.
Synonyms
alone solitarily independently solo unaccompanied single-handedly privately
Antonyms
together collectively jointly accompanied assisted collaboratively cooperatively