The virgin who planned to lose her virginity on her eighteenth birthday can talk, at the end of the letter, about how this was her best birthday ever. Or the trash collector can talk, at the beginning of his letter, about people's negative perception of his profession. Of course, at the end, after he's had hot sex with the new gal at 1234 Rose St., he can talk about how wrong all those people are. Keep in mind, as you write your letters, that every market is different. Each editor is going to have a different format, style and word count.
Some editors have strict formulas that they follow, and no deviation is tolerated.
Some want long letters that almost read like full length stories, some want a more colloquial approach. So, just like when writing stories, you must research your market. Read several issues of a magazine you'd like to write for, then send away for their guidelines. Only then should you send out a letter that you've crafted expressly for this market. If, however, you've already written the perfect letter but it doesn't quite conform to a particular editor's guidelines, don't despair.