Wiktionary
prep.phr. 1 alone; without assistance or help from others. 2 Alone, without another's company 3 (context rare English) (&lit by oneself English)
Usage examples of "by oneself".
What one cannot do by oneself in this life, because there are things which one cannot ask, nor do, nor wish, nor learn by oneself, one can do in company, and without needing to be Thirteen, as in Balzac's story, or Four, as in The Three Musketeers.
I know for a fact that it takes a lifelong struggle to be by oneself in the world of power.
One gets very wary and wide-awake when one has to manage a team of eleven dogs and a sledge load by oneself, but it was a most interesting experience, and I had a delightful leader, “.
It is the token of a humble spirit always to do well, and to set little by oneself.
It was best, of course, if Mma Ramotswe was there too, as they could exchange news and opinions, but it was still enjoyable to be by oneself, turning the pages of the magazine with one hand and licking the sugar off the fingers of the other.