To bless someone, in the most literal sense of the word, is to confer your hopes to them.
That's why so many traditional blessings begin with the word "may."
Take, for instance, what is perhaps the best-known Irish blessing (or toast, as the case may be this time of the year):
May the road rise up to meet you.
May the wind be always at your back.
May the sun shine warm upon your face;
The rains fall soft upon your fields and until we meet again,
May God hold you in the palm of His hand.
"May" doesn't mean "so be it." May implies that something is possible, but not a done deal. May hopes that God puts it in play and that you get out of your own way and allow it to happen.
John O'Donohue, the great contemporary Irish poet/philosopher (and former Catholic priest), knew the power of "may."