Okkkkkkkk.... this is my little help for you;
However, most of them have taught me the real meaning of many things that were once abstract to me, for instance a panic attack.------------ I suggest you to remove the example from this sentence.... You are going to talk about it in the next para. Here's my suggestion;However, most of them left me with a clear understanding of many things that were once only abstract ideas for me.
My father was sailing those troubled waters(no comma) on that day, while at home normal routine continued and I prepared for my final board exams of class
Here the plural form of water is fine... Its a phrase ; troubled waters : ) ...and here it gives a more poetic mood : )
You also say - Still waters run deep :)