Romantics have a hard time facing up to the fact that affairs occur and not all that infrequently. If the suspicion is suddenly aroused, a relationship that appeared healthy is suddenly unsteady and in the process it often emerges that the reason for the infidelity lies somewhere in the past. One of the partners had long since begun to distance himself or herself from the other. But it doesn't have to go that far.
Little signs in everyday life can indicate that one partner is starting to pull away from the other. Sometimes the distancing is obvious.
"When one partner busies himself or herself alone all the time and avoids encounters with the other partner, that can mean that he or she internally is dismissing the relationship," said psychologist Michael Mary of Schadeland in Germany's northeast state of Mecklenburg-Vorpommern.
Clearly stated, this means that when a lover pursues his own interests almost exclusively, when he is on the telephone for hours, discussing things that his partner knows nothing about then there is danger ahead. It's also a clear sign, if he has started looking for new friends on the Internet.
But it's not always easy to spot because nobody, despite all the confidence of a relationship, can see into the other's heart.
"People search for perfection in their relationships," said Eva-Maria Zurhorst, a couple's counsellor in Wuppertal. When one partner has the feeling something is missing, he tries to fill the vacuum - and sometimes he looks outside the relationship for what's missing. Having an affair is, after a while, only a few steps away, and the other partner initially doesn't know anything about it.
Even when everything appears to be going well, men and women still cannot be sure. That is the experience of Erika Berger of Cologne, who works at a sex talk service. There are banal reasons for people to sexually break out of their relationships, she said.
"There are people who have never had any great experience sexually. In their case, curiosity and the fear of missing something are very big things," Berger said. Others seek confirmation and for that reason are interested in "new contacts."
But sensitive people can tell when his or her partner has been active elsewhere, said Berger. Women in particular have a sixth sense in this regard.
"When men all of a sudden are much more attentive or bring flowers or presents for no reason, we prick our ears," said Berger. If these sudden gifts are combined with late nights in the office and out-of-town appointments, for many women the situation is clear. But bad behaviour is not just a men's thing.
"Men often notice a bit late when their partner is getting her kicks somewhere else," Berger said, adding that this is something she has established in conversations with men in that situation. "Women who have affairs are more sneaky and plan events precisely out in advance."
An alarm should sound if a partner has no desire to have sexual intercourse and always finds excuses not to do so. As long as the partner does not admit to the affair, it remains just speculation. Only an open discussion can return a sense of security.