What did roosevelt mean when he said . but justice and generosity in a nation . . count most when shown not by the weak but by the?

no people on earth have more cause to be thankful than ours, and this is said reverently, in no spirit of boastfulness in our own strength, but with gratitude to the Giver of Good who has blessed us with the conditions which have enabled us to achieve so large a measure of well-being and of happiness. To us as a people it has been granted to lay the foundations of our national life in a new continent. We are the heirs of the ages, and yet we have had to pay few of the penalties which in old countries are exacted by the dead hand of a bygone civilization. We have not been obliged to fight for our existence against any alien race; and yet our life has called for the vigor and effort without which the manlier and hardier virtues wither away. Under such conditions it would be our own fault if we failed; and the success which we have had in the past, the success which we confidently believe the future will bring, should cause in us no feeling of vainglory, but rather a deep and abiding realization of all which life has offered us; a full acknowledgment of the responsibility which is ours; and a fixed determination to show that under a free government a mighty people can thrive best, alike as regards the things of the body and the things of the soul.