Dreams are not meaningless, and they are certainly not useless. For a start, they are crucial for processing emotions. "Dreams modulate the emotions - they keep them within a certain range," says Patrick McNamara of Boston University. New research has found that naps consolidate emotional memories - and the greater the amount of rapid-eye-movement (REM) dream sleep, the greater the processing of these memories.-- from 10 Mysteries of you: dreams.
Julia Whitty notes that the Tibetan Buddhist Lama Tenzin Wangyal Rinpoche advises us to look at our experience of sleep to discover whether we are truly awake.  She quotes this:
...every day ends the same. We shut our eyes and dissolve into darkness. We do so fearlessly, even as everything we know as "me" disappears. After a brief period, images arise and our sense of self arises with them. We exist again in the apparently limitless world of dream. Every night we participate in these most profound mysteries, moving from one dimension of experience to another, losing our sense of self and finding it again, and yet we take it all for granted. We wake in the morning and continue in "real" life, but in a sense we are still asleep and dreaming. The teachings tell us that we can continue in this deluded, dreamy state, day and night, or wake up to the truthThe Bon tradition, Whitty writes :
teaches a yoga of dreams and sleep wherein, among other things, practioners learn to consciously dismantle the scaffolding. This work is done in the course of lucid dreaming, which students learn to cultivate at will. Since dreams are free of the rational mind, they reveal our true level of awareness and can provide an alternate and possibly speedier pathway to a clearer life. Although Western psychology believes dreams should not be tampered with, since they carry messages from the subconscious, Buddhists think differently. According to Tenzin Wangyal Rinpoche, "it is better for the aware dreamer to control the dream than for the dreamer to be dreamed".As W.B. Yeats put it, "in dreams begins responsibility."
 The Fragile Edge, page 213
 ibid page 226