“God strengthens me,” and “God is my strength" a Vital Difference

Elijah the Tishbite by Friedrich W Krummacher 

"If God strengthen me, then, through his grace, I experience within me a Divine power, by which I can accomplish something, and feel myself arrayed and armed with a courageous and joyful spirit; I smile at partition-walls that would confine me, and at barricades that would exclude me, and I fear nothing.

But if, finding nothing but weakness in my soul, and trembling at the sight of the danger that surrounds me, and at the immense mountains of difficulties which lie before me – yet, with all the shrinking of nature, I advance with holy boldness to meet them, hoping on against reason and feeling, in simple faith on Him who is eternally near, who will go with me, and to whom it is an easy thing to rebuke, with a word, the ocean’s waves, and to thrash the mountains so that they shall become a plain; and if I walk by faith on the waves of nature’s terrors, destitute of courage and yet a hero, out of weakness made strong, and out of despondency valiant – then I can exult and say, “God is my strength;” and my feet are placed upon a rock. What a wonderful thing is faith, which lays hold of a power to do all things, through Christ strengthening us; which brings man, who is a worm, into fellowship with the Father and with his Son Jesus Christ, and is the means whereby strength is ordained, and praise perfected out of the mouth of babes and sucklings!"