I don't know why anyone would down-vote your question. It is valid. And important. I am glad you brought it up.
Can I ask a few questions first, do you want to change your social and familial situation? Have you always been pretty much "solo" or is this a change? Can you share your age (approx.) and type of living situation (rural, urban, suburban)?
As for a broad answer, there are two ways to find meaning and happiness in life - one is through relationships that are loving (and personal) and another is through relationships of service (to society).
If you like being solo most of the time, you can still build relationships (and meaning) by finding organizations and helping them. You can volunteer at races, in churches, in your city, or other similar places. At least this way you are not "on your own" all day, every day.
And there is a good chance after a while you will build relationships with these people...
EDIT: Were you asking how to be happy without relationships (just with yourself)? If that was the case, you might consider becoming a modern stoic. They seemed to be pretty good at that kind of thing! Stoics are in these days!