Tikhon was in graduate school in theoretical physics, when he read Paul Graham's essay on How to Start a Startup. Inspired by what he saw, Tikhon applied, not at all sure that he would get in, but once accepted, Tikhon dropped out of grad school and moved to Cambridge, where YC was based at the time. The rest is history!
Not knowing much about what they were doing early on, Tikhon and team found feedback from the Y Combinator team to be incredibly useful. They would look at the Scribd's progress and be able to immediately steer the guys in the right direction, saving them invaluable time in wasted effort.
A lot of successful founders had started as solo founders, and Tikhon says that startups are already hard, and if you are willing to persevere on your own, that only shows an additional strength of character.