Buddhist, how can an agnostic-atheist person reach enlightenment is it possible?

My life has its issues but it is great & i'm mostly happy. If I don't suffer, how can I reach enlightenment or Nirvana. I mostly DO NOT harm anyone, I am vegan, i don't harm myself with any intoxicant, and I deny all super natural things. So can I still reach Nirvana or 'extinct' ?