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 10th10 .
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 :)