This prayer is about the right attitude towards illness.
March 17, 1914
AS soon as physical conditions are a little difficult and there results from them some unease, if we know how to surrender completely before Thy will, holding cheap life or death, health or illness, our integral being enters immediately into harmony with Thy law of love and life, and all physical indisposition ceases, giving place to an ease, calm, deep and peaceful.
I have noticed that if we enter into an activity which requires a great physical endurance, what fatigues the most is the anticipation in advance of all the difficulties to which we shall be exposed. It is much wiser at every moment to look only at the difficulty of the present minute; this makes the effort easier because it is always proportionate to the sum of force, the resistance we command. The body is a marvellous instrument, it is our mind that does not know how to use it, and, instead of promoting its suppleness, its plasticity, puts into it a certain fixity arising from preconceived ideas and unfavourable suggestions.
But the supreme science, O Lord, is to be united with Thee, to confide in Thee, to live in Thee, to be Thou, and then there is nothing that is impossible to the man manifesting Thy omnipotence.
Lord, my aspiration rises towards Thee like a silent canticle, a mute adoration, and Thy divine Love illumines my heart.
O divine Master, I salute Thee.”
The text above is quoted from the Third Edition, 1954 (translation by Rishabhchand Samsukha)
This book is freely available at https://www.auro-ebooks.com/prayers-and-meditations-1954-edition/