To meditate, you should withdraw
within yourself or retire to a secluded
corner or to the forest. And you should
always discriminate between the Real
and the unreal. God alone is Real, the
Eternal Substance; all else is unreal,
that is, impermanent.
By discriminating thus, one should
shake off impermanent objects
from the mind.

Shri Ramakrishna Paramahansa