Love doesn't sit there like a stone, it has to be made, like bread; remade all of the time, made new.I have been unable to verify who the original author is. The page-a-day calendar credits Ursula K. Le Guin, one of my favorite authors, whose style is certainly consistent with the quote. But in trying to find where she said it, I discovered competing attributions of the same quote to Og Mandino. (There's even this page, which attributes it to both, though it credits Le Guin with more variants of it.)
I don't know how to resolve the question. I really wish those sites that deal in quotations would provide more details - where they said it and when, or link to someone who does give those details. After all, I think writers should get appropriate credit for their words. In this case, I suspect one of these two writers quoted the other, and subsequent readers misattributed the words. For what it's worth, my guess is that Mandino is the original, and Le Guin quoted him because she loved the sentiment. That's only based on the fact that he was born earlier (1923 rather than 1929), and has already died (1996), so statistically he may have got around to saying it first.
But, at another level, it doesn't really matter. After all, I share quotes not because I want to connect myself to famous people, nor because I want to help increase their fame. I share them because I find the sentiments valuable - because they reflect or affect my own sentiments.
Anyway, take what lesson you like from this attribution dilemma - the quote itself is wonderful.