THE WORD blessing has come to mean more often than not a pious formality such as ministers are continually being roped into giving at high-school graduations, Rotarian wienie roasts, and the like, and to say "God bless you" to a person, unless that person happens to have just sneezed, is generally regarded as a pious eccentricity. It was not always so.
In the biblical sense, if you give me your blessing, you irreversibly convey into my life not just something of the beneficent power and vitality of who you are, but something also of the life-giving power of God, in whose name the blessing is given. Even after old, half-blind Isaac discovered that he had been hoodwinked into blessing the wrong twin, he could no more take the blessing back and give it to Esau than he could take the words of it out of the air and put them back into his mouth again.
Religious language has come to such a pass that perhaps "luck," of all words, suggests the reality of this better than "blessing." Everybody knows that luck has magic in it and that when you have it, you really have something. It may see you through hard times. It may win you the sweepstakes. A blessing, on the other hand, has come to seem something on the order of a Hallmark friendship card.