by ourselves

by (oneself)

1. Alone. Because there's usually so much going on with the kids, I really enjoy spending a quiet Saturday night by myself.
2. Through one's own efforts alone. You can't move that table all by yourself! Here, let me help you. My little girl loves to get dressed by herself, so tutus and cowboy boots have become the norm around here.
See also: by
Farlex Dictionary of Idioms.

by ourselves

 
1. with no one else present; alone. Do we have to sit here by ourselves? Can't we sit with Mary and Max? We like to eat by ourselves, so we can talk about private matters. 2. with the help of no one else. We can do it by ourselves. Can we lift this by ourselves, or do we need some help?
See also: by, ourselves
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • at will
  • at the end of (one's) fingertips
  • be hoist by (one's) own petard
  • be hoist with (one's) own petard
  • be hoist with one's own petard
  • be hoist/hoisted by/with your own petard
  • be on (one's) pat
  • at (one's) doorstep
  • at doorstep
  • a ball and chain
References in classic literature
or find us by ourselves, seeking entertainment in yelling, and sobbing, and rolling on the ground, divided by the whole room?
Wuthering Heights
To an extent that can be true, because there are times that things become really tense and we'd much rather be at home by ourselves not doing anything at all to do with music.
Bloc party
Being a professional drag performer myself, I agree that we need to get back to making films with and about drag queens for ourselves and, more important, by ourselves. When we leave the portrayal of drag to straight, mainstream Hollywood, they never quite get it right.
No shame
And so our brand economy discloses a task for spiritual maturity: knowing and being known by ourselves and others, without being governed by what we buy.
6 ways to be a conscientious Catholic consumer: Tom Beaudoin looks at our "branded" economy and says it's time to integrate who we are with what we buy