I can't feel any real sympathy for Sauron. He didn't stumble into his troubles in life; he made choices that led him to them. If he felt tormented by the loss of the Ring... well, he should've thought of that possibility when he made the thing in the first place. Narrowness of vision does appear to be one of Sauron's problems (made worse by hubris). As he couldn't envision anyone else wanting to destroy his Ring, he probably couldn't imagine anyone being strong enough or lucky enough to take it from him. One would think that feeling torment over its loss would've led him to learn to consider all the possibilities of what might occur should it fall into the hands of his enemies, but it clearly didn't.
I agree with Morth, he's a dry piece of toast, and worse. He had the example of Morgoth from which to learn, and to some extent he did, but he didn't learn that he should never underestimate his enemies, or the vagaries of "luck," as it is called. He made his Ring to be the Ultimate Weapon that would enable him to rule the world, he got walloped twice while in possession of it, and still didn't stop to consider all possibilities when facing another war without it. If I feel any pity for him, I suppose it's because for a fearsome Dark Lord, the guy just isn't all that bright.
