The word is my favorite for those reasons, and more.
Because its unregularly use? I don't think until that moment you have say a single reason?
Often I will find myself in a hurry or stressed about something, whether it is school, work, family, friends, or athletics,
this is when I wish I could achieve complete serenity.Of course, such a goal is unachievable as stress is part of human nature. Sometimes stress can even help a person,
This seems contradictory since stress is kind of opposite to serenity and you should talk about how good serenity is.
You definitely need to rework on this, try to order your ideas and them write them. Also, look for a strong final sentence, THAT'S VERY IMPORTANT!
Hope it helps!