A marriage can still be saved even if one or both spouses have cheated on each other, as long as the spouses allow God back into their lives and show true repentance, Pastor Shane Idleman said.

Idleman blasted adultery as pure "selfishness at its core" since it destroys not only marriages but also parenthood, friendships and even family ties.

"Adultery moves us from the altar to the courtroom—transforming a couple, once deeply in love, into bitter enemies. Hopes and dreams for the birth of a child, now twisted, become a nightmare for innocent children," he wrote in an opinion piece for Charisma News.

Adultery makes spouses, who once felt loved and cherished, feel insignificant and discarded, said Idleman.

Children are gravely affected since they feel they're to blame for their cheating parent's infidelity, thinking that they aren't good enough for their parents, that's why they became unfaithful to each other and sought the affection of another person outside their family, Idleman said.

The ultimate goal of sexual sin is to destroy marriage, the pastor said, adding that this is best tackled by the Bible verse James 1:15: "Then, when lust has conceived, it brings forth sin; and when sin is finished, it brings forth death."

But even though adultery hardens the hearts of once loving spouses and makes the children feel miserable, Idleman said there is still hope for their marriage to survive—and even thrive—just as long as the couple turns to God and be mindful that reconciliation is often prevented when complete separation does not happen and when genuine repentance does not occur.

"Reconciliation is nearly impossible if complete separation does not occur between those involved in adultery," Idleman said. "Completely stepping out of the other person's life to see where God will lead is the only way to clear vision," he explained.

When adulterous relationships begin, the adulterer is often more concerned about the feelings of the one he or she is having an affair with rather than the feelings of his or her spouse and family, he said. That is why it's important for the aggrieved spouse to step out of the picture, even for a while, he added.

The second thing that would surely destroy any marriage is if genuine repentance does not occur, Idleman said. "Many are sorry about adultery, but being sorry is not enough. Only genuine repentance opens the ears of God and restoration," he explained, adding that the difference between being sorry and being repentant is akin to "being caught" and "coming clean," respectively.

All hope is not lost for couples facing this kind of problem, Idleman said, adding that past mistakes all have consequences, but it all depends on how people deal with them.

"The pain of adultery can make us bitter, or it can make us better—ultimately, it's our choice," he said. "God can restore a damaged marriage if genuine repentance and forgiveness take place. True repentance is unconditional and takes full responsibility for wrongs done. A truly repentant person is desperate to be forgiven, to focus on what he or she has done rather than placing blame or responsibility on others."