A study conducted in South Korea found that strict boundaries in marital intimacy are highly stressful for men. When women, in an effort to conceive, pressure their husbands to have sex during ovulation and refuse to have sex during safe periods, this can lead to unpleasant consequences: decreased potency, infidelity, and even abandonment.
This is explained by elevated levels of cortisol, a stress hormone that reduces testosterone production, in a man's blood. This causes a decrease in libido, which then leads to a vicious cycle: attempts to become parents are doomed to failure, a man's self-esteem plummets, and to regain his sense of macho self-worth, he seeks new relationships.
To avoid this unpleasant situation, experts recommend not focusing on the days favorable for conception, but simply having sex more often.