This has always been a problem for me. I used to think it was a sides-effect of the dysfunctional home that moved, on average, every three months that I grew up in. I knew I developed coping skills that put a wall between me and others. You can only say good-bye to friends so many times before you stop getting close enough to care that you are saying good-bye.
Then I had kids and saw much of my own personality reflected back at me, but in different ways and degrees. At that point, I realized I probably always would have had difficulty making friends and would probably only had a couple friends. My upbringing made that worse, but wasn't likely the entire cause.
Now, I find that I don't know how to get around that. Articles everywhere say, "meet with people", but I feel more lonely in those situations because I don't know how to break into the conversation. Depression makes it worse, because you are constantly asking yourself, "why would they even want to know about me?" There's only so many times you can go to the entrepreneur meet-up and not talk to people (even after presenting) before it starts doing more harm than good.
I agree with the article that connecting with other people is of number one importance to fighting depression. I would really like to find the guidebook for doing that. :/