I realized I was responsible for myself around ten years old, when my father kicked me out of his house. The thought of dependency was subsequently abhorrent to me, but I couldn't do anything about it at the time due to depression. Since walking out of that a year and a half ago, my self-responsibility (humorously like a delayed-blast fireball spell, if anyone is familiar with D&D) has triggered massive waves of motivation to be very, very good at everything I could be good at. I am almost completely self-sufficient and quite happy for it; I have a much greater appreciation for small things and personal growth now.
Because of self-reliance, I stopped expecting anything from others and focused on my own projects and journeys. This is not to say I was selfish - I've logged ~200 volunteer hours at various homeless shelters and kitchens since that year and a half - merely that preoccupation with self-improvement often kept me away from others, until recently. I now have two awesome introverted friends who I rely on for soft evenings, laughs, easy companionship, and a feeling of close-knit community.
*Shrug* I am still quite young and my story is slowly unraveling.