A teaching on prayer from the Baal Shem Tov, Amud Hatefillah.
Before praying one should always think that he is ready to die in that very prayer, so great should his concentration be. He should not only be ready, but his concentration should be so great that after speaking a few words before G!d, may His Name be blessed, that he actually risks his life. Then he will say in his heart, why do I think so much of myself, when after a mere few words before Him I could pass away? Then he will know what a great kindness it is from G!d, that He gives him strength to finish the prayer and live.
It’s told that Uri of Strelisk would put his house in order and kiss his wife and children goodbye every time he went to pray, so vividly did he feel that he might pass away in his prayer. I’ve thought I might die of boredom before… I hope someday my davening can be this kind of near-death experience.