If this were my PS, I would start it in this way.
I would have an attention grabbing sentence, one that captivates my reader;
Perhaps a scene from my life, or some shocking dialogue.
If this were my PS, I would use it to tell a story.
I would create it in a way that shows some larger theme, one that may not actually have been obvious when the event happened.
Yet, if this were my PS, the act of brainstorming, creating, and writing about that theme would actually teach me something new about myself.
If this were my PS, I am not sure what I would talk about.
But if this were, in fact, my PS, I know that I would eventually find something interesting to say (I hope).