I haven't done a lot in the big scheme of things but even still, I get an occasional PM from someone who tells me something I said or wrote that is archived on the Internet helped them. Yeah, one person can make a difference, and often does.
That said, is it ever REALLY just one person? Links to the stuff I did are hosted on someone else's ex-JW site. The letter you obtained, apocalypse, was printed in someone else's book. Those are just two examples of individuals making a difference but with cooperation and assistance from others.
It takes individuals AND it takes cooperation.
Work to help others and keep paying it forward, everyone.