By Oneself Meaning

(rare) Used other than as an idiom: see by,‎ oneself.

Example: Alone; without assistance or help from others.
  I have always wondered why shoe salesmen think I can't tie my shoes by myself.
  You ate the whole thing by yourself?
Alone, without another's company
  He sat by himself in the corner, waiting quietly.
  He kept the gun by himself at all times.