IDIOMS

on one's lonesome

(idiomatic) Alone; without aid or accompaniment.

Example: 1996, Joan Jonker, Sweet Rosie O'Grady, ISBN 9780755391981 (2012 Headline ebook edition), Google books online:
  "Sittin' there all on her lonesome the whole day long, it's understandable she gets down in the dumps."
2003, Aaron P. Frank, Honda Motorcycles, ISBN 9781610609586, p. 176 (Google preview):
  But his skills with a bike were unassailable — while the factory teams were struggling with setup, it was Dunlop on his lonesome that gave the company its first International victories.
2015, Josephine Myles, Scrap, ISBN 9781619224926, ch. 10 (Google books online):
  Working on his lonesome every day definitely had him craving a bit of human company.