This has to be remembered, that "I am real." This has to be remembered, that "I am the only certain reality -- everything else may be, or may not be."
We never look inwards for this absolute reality; and we go on living a life without basing it on this rock of certainty. Hence our lives are just castles in the air, or at the most, sandcastles; signatures made on water -- you have not even completed it, and the signature is gone. Our lives are like that -- one moment we are here, another moment we are gone, and that moment could have been used for self-remembering.
Only people who use their life for self-remembering are using this great opportunity.