A person at prayer is like a bed of coals.
As long as a single spark remains,
a great fire can again be kindled.
But without that spark there can be no fire.
Always remain attached to G-d,
even in those times
when you feel unable to ascend to Him.
You must preserve that single spark–
lest the fire of your soul be extinguished.
Liqqutim Yeqarim 15b & Keter Shem Tov 37b-38a, as edited and translated by Arthur Green & Barry W. Holtz in YOUR WORD IS FIRE: The Hasidic Masters on Contemplative Prayer (1993) at page 112.