One of the best I've read:
Sincerely, One of Many Girls Who Care
Written by Anna Koistinen
Found on Anna Koistinen - In the Hands of the Potter
Are you a boy?
Not sorry that you’re a boy… That’s awesome.
I’m sorry that you see hundreds of advertisements every week showing half-dressed women.
I’m sorry every time you go to the beach or your neighborhood pool you can’t look in any direction without seeing a girl basically in her underwear.
Or that you can’t scroll through Instagram on “women crush wednesdays” or any day for that matter without an airbrushed girl in a thong staring you down.
Or that your buddy showed you that one magazine when you were 9 and you’ve never forgotten that moment because that was the first time you first saw a completely naked woman.
When I think about the guys in my life who are striving to live with a pure and Godly mindset, it honestly breaks my heart that they’re surrounded with so much temptation.
I think about my 22 year old brother, David, and the fight he is fighting every day for his future wife.
I think about the middle school boys in my youth group who don’t seem to have a clue how destructive this lustful lifestyle they are checking out is.
But most of all, I think about the man I’m going to marry.
Not only are you surrounded with a world that’s obsessed with worthless, cheap sex and relationships that mean nothing outside of sexual appeal, you’re encouraged to take part in seeing women as only objects of sex and instant pleasure. All the sports reporters are drop dead gorgeous. All the news anchors. Any girl that’s used for any kind of advertising. I wouldn’t be surprised if its all you can think about.
Its like every guy judges you based off of how hot your girlfriend is.
And maybe you’re so consumed with trying to be a “man” that you’d put up with the most annoying, possessive, selfish girl if she was really hot. Because that’s all that really matters right?
Or maybe you’re not putting up with a girl right now who really isn’t annoying, possessive, and selfish. Maybe you’re with a really sweet and pretty girl but you know deep down inside, if you’re honest, she’s not striving after God nearly the way she’s striving after you. You can’t fulfill the role of God for her. That’s just not fair for you and definitely not healthy for her.
And I haven’t even tapped into pornography.
Porn. The fantasy world where men’s desires are cast as first and foremost the most important thing in the whole world. And where women are cast as objects of sex and instant pleasure in order to fulfill that need at anytime, in any way, with any women you could dream of. An industry where both women and men are lied to about their health safety, and usually take drugs to suppress the emotional trauma that happens on set. Where over 121 porn stars have died from aids, suicide, homicide, drugs, and premature death since 2007. 
Porn. What 50% of men and 20% of women IN THE CHURCH look at regularly. 
Where according to the American Academy of Matrimonial Lawyers, 58% of divorces were a result of a spouse looking at excessive amounts of pornography online in 2003. 
Porn. The industry that makes over $97 billion revenue worldwide, $13 billion in the U.S. alone.
…which is more than the revenues of the top technology companies combined: Microsoft, Google, Amazon, eBay, Yahoo!, Apple, Netflix, and Earthlink
…which is more than NFL, NBA, and MLB’s revenues in 2012 combined.
Pornography destroys. It becomes an addiction and distorts the way you see your sisters in christ, and eventually your wife.
But enough with the pity party I’ve managed to throw for you.
(...Read more of this letter on her blog)
I felt this was a great reminder to all of us that relationships aren't about our bodies when it comes down to it.