When you are alone you are not alone, you are simply lonely - and there is a tremendous difference between loneliness and aloneness. When you are lonely you are thinking of the other, you are missing the other.
Loneliness is a negative state. You are feeling that it would have been better if the other were there - your friend, your wife, your mother, your beloved, your husband. It would have been good if the other were there, but the other is not. Loneliness is absence of the other.
Aloneness is the presence of oneself. Aloneness is very positive. It is a presence, overflowing presence. You are so full of presence that you can fill the whole universe with your presence and there is no need for anybody.
Osho The Discipline of Transcendence, Volume 1 Chapter 2