Take special care of the soul of salah i.e. from the beginning till the end of salah, maintain full concentration and sincerity.
Whatever you utter with the tongue, and whatever actions you perform with the limbs, bring its effect into the heart as well. This means that when your body bends for ruku’, then bend the heart with humility, when you utter Allahu-Akbar (Allah Ta’laa is the Greatest) with the tongue, this feeling should pervade the heart, that definitely there is nothing greater than Allah Ta’laa, when you recite Al-hamdulillah (All praises are solely for Allah Ta’laa), then your heart should be filled with gratitude for Allah Ta’laa’s Favours, and when إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ (Only You do we worship and only You do we seek assistance) emerges from the tongue, then at that time your feebleness, worthlessness, and neediness, i.e. this feeling should be found in the heart that besides Allah Ta’laa, neither do I, nor do anyone else, have control of anything.