Marriages can survive infidelity, Marshall said, but a few things have to happen first.
Offending party has to be sorry. "He [or she] has to be willing to repair the damage by showing remorse," Marshall said.
Admit the affair and why it happened. "If you can't articulate it, how can you fix it?" she said.
The offender must make a plan to fix the problem.
Gillies said repairing the relationship requires both parties, however.
"It's a complex situation," she said. "I think it's important also when somebody does something that's socially unacceptable like an affair. The person who has had the affair happen to them can sort of put a halo on and say, 'You did something really bad.' It's important for both partners to look at how they work together.
"One person can't be a devil and the other can't be an angel," she said.