Research tells us that approximately 20 percent of people in supposedly monogamous relationships will cheat on their partner at some point during the relationship. Interestingly, the reasons for cheating often differ by gender. Most of the time, regardless of gender, cheaters have plenty of justifications and rationalizations that make their behavior OK (in their own minds).
Men in particular tend to engage in all sorts of “denial” when it comes to infidelity—blaming, minimizing, justifying, rationalizing, etc.: