Excerpt from Bhakti Yoga - Swami Vivekananda

The mind should always go towards God. No
other things have any right to withhold it. It should continuously think of
God, though this is a very hard task; yet it can be done by persistent
practice.  What  we are now is the result of our past practice. Again,
practice makes us what we shall be. So practice the other way; one sort of
turning round has brought us this way, turn the other way and get out of it
as soon as you can. Thinking of the senses has brought us down here — to cry
one moment, to rejoice the next, to be at the mercy of every breeze, slave
to everything. This is shameful, and yet we call ourselves spirits. Go the
other way, think of God; let the mind not think of any physical or mental
enjoyment, but of God alone. When it tries to think of anything else, give
it a good blow, so that it may turn round and think of God. As oil poured
from one vessel to another falls in an unbroken line, as chimes coming from
a distance fall upon the ear as one continuous sound, so should the mind
flow towards God in one continuous stream. We should not only impose this
practice on the mind, but the senses too should be employed. Instead of
hearing foolish things, we must hear about God; instead of talking foolish
words, we must talk of God. Instead of reading foolish books, we must read
good ones which tell of God.