How to know you have attained the Self
Do your work nonchalantly spontaneously and unpremeditatedly and then quietly flows your river Don. Do not meditate or do yoga and you have attained the Self. You are not attached to anything whatsoever not even God.
I would like to believe that the Purusho talked about in Hinduism is what they named as the Self.
There is the highest possible level of ananda/bliss in Self when one knows each moment of the passing day that one has acted correctly as one's karma with the person being classified as purushouttama.