It's from the 1600s, but I guess it's a "Christian classic" (which means people still read it even though it's really old.)
Anyway, here are a few quotes...
Brother Lawrence said that the worst that could happen to him was to lose that sense of God which he had enjoyed so long. Yet the goodness of God assured him He would not forsake him utterly and that God would give him strength to bear whatever evil He permitted to happen to him. Brother Lawrence, therefore, said he feared nothing
"When I fail in my duty, I readily acknowledge it, saying, I am used to do so. I shall never do otherwise if I am left to myself. If I do not fail, then I immediately give God thanks, acknowledging that it comes from Him."
We ought not weary of doing little things for the love of God, who regards not the greatness of the work, but the love with which it is performed.
Please recommend to him that he think of God the most he can in this way. It is very fit and most necessary for a soldier, who is daily faced with danger to his life, and often to his very salvation.
It seems to him (in fact, he feels it) that this God of love, satisfied with such few words, reposes again and rests in the depth and center of his soul.
I cannot imagine how religious persons can live satisfied without the practice of the presence of God. For my part I keep myself retired with Him in the depth and center of my soul as much as I can. While I am with Him I fear nothing; but the least turning from Him is insupportable. This practice does not tire the body. It is, however, proper to deprive it sometimes, nay often, of many little pleasures which are innocent and lawful. God will not permit a soul that desires to be devoted entirely to Him to take pleasures other than with Him. That is more than reasonable.
You need not cry very loud. He is nearer to us than we are aware
I do not advise you to use many words and long discourses in prayer, because they are often the occasions of wandering. Hold yourself in prayer before God, like a dumb or paralytic beggar at a rich man's gate.
We must know before we can love. In order to know God, we must often think of Him. And when we come to love Him, we shall then also think of Him often, for our heart will be with our treasure.
You would think it rude to leave a friend alone who came to visit you. Why, then, must God be neglected? Do not forget Him but think of Him often. Adore Him continually. Live and die with Him. This is the glorious work of a Christian; in a word, this is our profession. If we do not know it, we must learn it.
I do not pray that you may be delivered from your pains; but I pray earnestly that God gives you strength and patience to bear them as long as He pleases. Comfort yourself with Him who holds you fastened to the cross. He will loose you when He thinks fit. Happy are those who suffer with Him. Accustom yourself to suffer in that manner, and seek from Him the strength to endure as much, and as long, as He judges necessary for you.
He never forsakes us until we have first forsaken Him. Let us fear to leave Him. Let us always be with Him. Let us live and die in His presence. Do pray for me, as I pray for you.
Let all our efforts be to know God. The more one knows Him, the greater one desires to know Him. Knowledge is commonly the measure of love. The deeper and more extensive our knowledge, the greater is our love. If our love of God were great we would love Him equally in pain and pleasure.