Symbolism in "The Light of Other Days" by Thomas Moore is exemplified by the poet's memory bringing "the light Of other days around me:". In essence,his memory is shining a light on his past, whereby he remembers the vibrant and active times he enjoyed with family and friends involved in productive and youthful activities. The light of these other days are actually "remembrances", not actual light - so hence the symbolism here of good memories as a wonderful light.
The poet misses those who have died. He misses the laughter and tears of his youth as well. The poet feels alone without loved ones from his youth. He feels as if light has fled from his life as well. This symbolizes "joy" having fled his life as he carries on living without well-loved companions from his youth accompanying him on his life journey.