A. If the blessing were personal, implying, “Thank you, God, for giving energy to me when I am tired”, you might be right. But if you look at the previous two blessings you see a pattern emerging.
They praise God “who crowns Israel with glory” and “who girds Israel with might”. Like them, this final blessing, as the commentators point out, refers to the Jewish people as a whole. Though there are times when the people of Israel are worn out with oppression and tempted to lose faith in redemption, God assures us that He has not forgotten us and we should not lose our nerve or courage.
The blessing does not derive from the Talmud but its wording is Biblical, from Isaiah 40:29: “He gives power to the faint, and to him that has no might He grants strength”. The passage is part of the haftarah for Parashat Lech L’cha.