I know that for the right practice of it (the presence of God) the heart must be empty of all other things, because God will possess the heart alone; and as He cannot possess it alone without emptying it of all besides, so neighter can He act there, and do in it what He pleases, unless it be left vacant to Him.
There is not in the world a kind of life more sweet and delightful than that of a continual conversation with God. Those only can comprehend it who practise and experience it; yet I do not advise you to do it from that motive. It is not pleasure which we ought to seek in this exercise; but let us do it from a principle of love, and because God would have us.
Where I a preacher, I should, above all other things, preach the practice of the presence of God; and were I a director, I should advise all the world to do it, so necessary do I think it, and so easy, too.
Ah! knew we but the want we have of the grace and assistance of God, we should never lose sight of Him -- no, not for a moment. Believe me; make immediately a holy and firm resolution nevermore wilfully to forget Him, and to spend the rest of your days in His sacred presence, deprived, for the love of Him, if He thinks fit, of all consolations.
from The Practice of the Presence of God
by Brother Lawrence