Well, I do think it is a general trend in Tolkien's works, indeed.
Looking through all the books you can find a general rule pretty soon - if yor are humble, you win, if you are proud or arrogant, you lose. Simple as that, and I cannot think of any exceptions from any book right now, maybe some of you more wiser ones could point something out.
However, I very much doubt that it is a special thing of Tolkien's... thinking back to my childhood and reading Romanian fairytales it was pretty much the same. Usually the hero's older brothers went first on the quest, but due to their pride and arrogance they always failed at some point. The youngest brother however, the main character, always remained humble, no matter in which situation and always saw himself as serving others and not others serving him and in the end was repaid and saved the day.
I do however agree the case of Frodo is indeed out of ordinary. Whilst all the others from the Fellowship (ok, except Boromir) get repaid in one way or the other and live a happy and fulfilling life like Romanian fairytale heroes, Frodo ends up with nothing - he can no longer live in M-e and is forced to leave.
Why I think this happend is this:
Tolkien used the normal fairytale "any victory against evil will only come at a loss, will require a certain sacrifice". And since just letting Boromir die would not be a dramatic enough scene to justify the motto above, he needed to show how the quest damaged Frodo too. It was his sacrifice that gave all others the possibility to continue living on, but it was too late for him.
I actually wonder if that is something special about LotR, but I doubt it. I must admit I don't read a lot of other books, so I don't really know
, but maybe someone else can offer some other examples, I'm pretty sure there are some.
Ok, that's all, hope all that made sense, at least a little bit.
And btw, it's a pleasure to be posting on the BW forum again.