Non-duality is jnana; duality is samsara. If you can give up duality, Brahman alone remains, and you know yourself to be that Brahman, but to make this discovery continuous meditation is required. Don't allocate periods of time for this. Don't regard it as something that you don when you sit with your eyes closed. This meditation has to be continuous. Do it while you are eating, walking, and even talking. It has to be continued all the time. 

-- Final Talks.

PS: meditating = meditation on the Self (Atma Dhyana)