It's been compared to a river. As long as the passion stays within the banks, the river is good. But when it overflows the banks, then destruction can happen. Trust and confidence is shattered. There are hurts and pains that may leave lasting scars.
Future relationships can become difficult, perhaps even doomed, from the emotional trauma.
Future intimacies might be guarded, and the wonderful joys that God intends through our physical passions may never be as great as they could be. None of us have clean slates with respect to our sexuality. We have overstepped boundaries, if not in deed certainly in thoughts and fantasies. Some have more garbage back there to deal with than others do. Some of us have been abused.