My dear Father
As you are aware, I am not keeping well for quite some I have grown weak on account of hard work. Last week, I had fever. Though I have recovered considerably yet the weakness still persists and I am not able to exert much. I start feeling tired if I study continuously even for half an hour.
Consequently, I did not fare well in my last tests, as I was not able to devote proper time to studies. I am not able to concentrate in studies for long periods and hence may not be able to get good marks in the forthcoming half-yearly examinations.But, I assure you that as soon as I become physically fit and am able to concentrate on studies, I shall make up whole-heartedly and score better marks in my annual examinations.
I hope you understand my position and pardon me for neglecting studies.
Yours affectionately
Your loving brother