By going out into the real world.

Let me tell you, I used to be a doubt-riddled business owner, having started two businesses, overcoming quite a number of hurdles, dealing with every type of lunacy and drama you can think of.

But, when I went out to networking meetings (which usually are a huge waste of time and energy), started teaching workshops, met other entrepreneurs, it gave me confidence because I realized that a) my issues were hardly unique and b) I knew more than I'd ever thought compared to most other people in the general public who won't read, won't go to seminars or workshops, and never start businesses. Loneliness can be overcome by being humble, offering to volunteer where possible and applicable (where you're not being taken advantage of), and building friendships, strategic alliances with complimentary services, and remembering "what brought you to the dance."

Does that help?