Does it exist before we are born? Does it disappear when we die? It is unchangeable, or capable of growing/shrinking/strengthening? Can you lose your soul, or gain one?Answers to such a question are explicitly rooted in one's theology. Those are theological questions. Is there a soul? What is it? Depending on what one believes, those answers may be defined (by a faith's doctrines, or by authorities who've already weighed in...). Or not.
Unitarian Universalists, of course, don't have an easy out; we don't share a theology that defines these answers. Even if we've adopted an existing theological view, within the context of our UUism, that offers answers, that's something that we have to consciously adopt.
So what are my answers?
Well they arise from the things I've already concluded. I'm not a supernaturalist (and having said that, I think we actually know so very little that I'm entirely confident that there are things that look entirely supernatural...). I'm some form of pantheist. "This"--all of this that we see, touch, feel, experience (and the much, much greater part that we do not) is part of what I describe as nature. And that's all there is.
"Soul" is a term I use to describe that experiential essence of being; the "I" that seems to exist within a living being. Not the thinking, but the aware observer that experiences being aware and observing. Perhaps that is an illusion--but if so, it's a "real illusion," in the same sense that solid objects are illusions.
I tend not to believe in a soul as an entity that has a coherent existence separate from the living wave-form of a being. (But I'm entirely at ease with the idea of being wrong; it's something humans are particularly adept at--being spectacularly, flamboyantly, fervently wrong). It's a part of the universe, too. It, I suspect, ends with death. And just like matter, it doesn't go away. "Away" is a false concept. There's no away to go to. It just changes form. Matter decays into component materials and becomes other forms of matter--living or not. Energy goes off as well. The essential thing that is us doesn't remain coherently us; instead, traces of what we were end up smeared across the rest of the planet and all life and through the universe (given enough time).
It's an answer that's actually the same as other answers--it just depends on the perspective one takes on it. It's entirely possible to look at this and say "There's only one soul, and it's shared and interwoven through everything and everywhen." Which is about as good a metaphor for god as anything I've heard.
Can it die? No. Can it be squandered? Sure. Soul is--as best I can make out--'meant' to be exercised and enriched. Shared.