Concentration...

"To be constantly centered
on one's all perfect pure Self
is the acme of Yoga, Wisdom, and
all other forms of spiritual practice.
Even though the mind wanders restlessly
involved in external matters
and so is forgetful of its own state,
one should remain alert and remember;
the body is not 'I'.
'Who am I?'
Enquire in this way turning the mind
backward to its primal state.
The enquiry, 'Who am I?' is the only method
of putting an end to all misery
and ushering in Supreme Beatitude."

--Bhagavan Sri Ramana Maharshi--