Concentration is not thinking of one thing. On the contrary, it is excluding all thoughts, since all thoughts obstruct the sense of one's true being. All efforts are to be directed simply to removing the veil of ignorance. Concentrating the mind solely on the Self will lead to happiness or bliss. Drawing in the thoughts, restraining them and preventing them from straying outwards is called detachment (vairagya). Fixing them in the Self is spiritual practice (sadhana). Concentrating on the heart is the same as concentrating on the Self. Heart is another name for Self.
Ramana MaharshiYou are awareness. Awareness is another name for you. Since you are awareness there is no need to attain or cultivate it. All that you have to do is to give up being aware of other things, that is of the not-Self. If one gives up being aware of them then pure awareness alone remains, and that is the Self.
Ramana MaharshiTill you reach the state of jnana and thus wake out of maya you must do social service by relieving suffering whenever you see it. But even then you must do it without ahankara, i.e., without the sense of 'I am the doer', but with the feeling 'I am the Lord's tool'.
Ramana MaharshiThe master is within; meditation is meant to remove the ignorant idea that he is only outside. If he is a stranger whom you await, he is bound to disappear also. What is the use of a transient being like that? But so long as you think you are separate or that you are the body, an external master is also necessary and he will appear to have a body. When the wrong identification of oneself with the body ceases, the master will be found to be none other than the Self.
Ramana Maharshi