I am not the biggest John Piper fan in the world, but this article is quite good.  Speaking of sexual sin he says this.

The great tragedy is not mainly masturbation or fornication or acting
like a peeping Tom (or curious Cathy) on the internet. The tragedy is
that Satan uses the guilt of these failures to strip you of every
radical dream you ever had, or might have, and in its place give you a
happy, safe, secure, American life of superficial pleasures until you
die in your lakeside rocking chair, wrinkled and useless, leaving a big
fat inheritance to your middle-aged children to confirm them in their
worldliness. That’s the main tragedy.

He then goes on to write about how a understanding of forgiveness and justification is the weapon we use to move towards holiness and God’s great dreams for us.

As I see it, so many of the approaches taken with respect to sexual purity are based on works where as this is based on grace.

It is a good read…I would encourage you to check it out.

Source: http://www.desiringgod.org/ResourceLibrary/EventMessages/ByDate/1927_How_to_Deal_with_the_Guilt_of_Sexual_Failure_for_the_Glory_of_Christ_and_His_Global_Cause/

I found this via http://theologica.blogspot.com/2007/01/how-to-deal-with-guilt-of-sexual.html