That is the way Elijah felt. It provides no great amount of shade against the desert sun, but it is the best shade there is. Elijah is utterly at the end of his own courage and his own strength, and dejectedly confesses that in spite of all he has done at Carmel he is no better than his fathers. And he ate and drank, and lay down again. Elijah was so despondent that all he felt like doing was sleeping.
Many people when faced with difficult situations feel more tired and drained than usual.
They just want to sleep, hoping that when they wake up all their troubles will somehow have disappeared. God cared for Elijah and sent an angel to minister to him. He cooked bread and provided water and woke him up so that he could be strengthened and nourished. But Elijah didn't want to face another day and so retreated again into sleep. It may not be sleep.