"Prayer is the service of the heart." ~~ Talmud, Ta’anit
"You don’t have to pray loudly; just direct your heart to heaven." ~~ Rabbi Chia
"A man must bless God for the evil, just as he blesses Him for the good." ~~ Berakhot 9:5
"Redeem us speedily for the sake of Your name!" ~~ Eighteen Benedictions
"If a man sees that his prayer was not granted, let him pray again!" ~~ Talmud, Berakhot
"Unless we believe that God renews creation every day, our prayers grow habitual and tedious." ~~ Baal Shem Tov
"One who stands [in prayer] in Eretz Yisrael (the land of Israel) should direct his heart towards Jerusalem, if he was standing in Jerusalem, he should direct his heart towards the holy Temple. " ~~ Talmud, Berakhot 27a
"Prayers truly from the heart open all the doors in Heaven." ~~ Nachman of Bratslav
"The best weapons of Jew are his prayers." ~~ Nachman of Bratslav
"By benevolence man rises to a height where he meets God. Therefore do a good deed before you begin your prayers." ~~ Ahai Gaon, Sheiltot
"Who cries over the past is offering a vain prayer." ~~ Berakhot 9:3
"Prayer without intention is like a body without a soul." ~~ Yeshu’ot Meshicho