Discovering and trying to fill this "void" in wrong ways for all those years was one of the most essential realizations in my life. I used to attempt to fill it with drinking, all sorts of weird and secretive activities and affairs, and most importantly: endless mental activity, overthinking and overanalyzing everything constantly. Almost every activity I chose was overly intellectual while minimizing my most basic physical needs... always feeling learning yet another new thing, new expertise, new eccentric thought system, etc were an absolute necessity that would lead me to satisfaction eventually. Wrong, in my case. It is exactly the over-thinking and getting stuck in constant mental hyperactivity that has to be transformed for me. Balanced.
I am finding that I need to do a lot of hard self-work to change this pattern. Giving up the alcohol was actually one of the easier tasks compared with trying to change all the old ingrained, fear-based self-defenses. So what I am trying to do now is to take it simple for the moment: focus on my physical needs (diet, exercise, trying to set up a more regular schedule), connect with more people in "ordinary" ways, just try to live a more conventional life instead of all the eccentricities that had isolated me from the rest of the world so long.
Also, I am realizing more and more that the "void" is actually normal and does not necessarily need to be filled with substitutes that we artificially infuse with "meaning".... Just let it be, just view it. Buddhists ideas of emptiness have been helping me accept this... and meditation.
I think we all got to find our own ways to this universal feature of human nature...