I'm not necessarily calling out to the evil seductresses out there; this is also very helpful in cases of cheating on a boyfriend or girlfriend.
First- the bad =(
Let's look at the problems associated with adultry/ cheating.:
Proverbs 5:1-23 The description of the adultress and the desrtuction caused.
Proverbs 6:20-29 A warning against adultry.
Proverbs 6:23-35 The punishment.
Leviticus 20:10 More punishment. (There's a happy ending, just keep following)
Proverbs 7:1-27 A story of Adultry.
1 Corinthians 6:9-11 The kingdom of heaven is not for the sexually impure.
We've all made mistakes and, thankfully, we do have a way to escape the horrible consequences of adultry/cheating. We ALL deserve to go to hell, not just adulterers, but we don't have to.
1 John 1:9 "If we confess our sins, He is faithful and just and will forgive us our sins and purify us from all unrighteousness."
If you have been hurt by cheating or adultry,
Colossians 3:13 "Forgive as the Lord forgave you."
That doesn't mean you have to be stupid. Forgive them, everyone makes mistakes, just like you do, but, if it's an unhealthy relationship, forgive then move on to a Godly partner.
Finally...The Good Part
In the right context (marriage) sex can be a wonderful experience.
God doesn't condemn sex, He invented it!! He wants us to be happy, in a healthy relationship, sharing our lives with the person He wants us to be with.
Here's a beautiful description of sexual love in marriage:
Song of Songs 2 (seriously, that's the name a book in the Bible.)