If one partner feels unloved, unaccepted, disrespected, dismissed, or unimportant, one might find themselves seeking love and validation somewhere other than with the primary partner.
This can create angst, low self-esteem, guilt, deception, lies and emotional and sexual affairs. It is human nature to want to be loved, unconditionally accepted, affirmed, validated and heard. If these main desires are being unmet in one's primary relationship, one may stray. This sometimes happens intentionally but mostly unintentional attention is paid to another person and they begin to fell alive and loved.
How can you avoid this happening in your marriage? Do you display genuine love and affection to your partner on a daily basis? Do you go out of the way to do special tasks for your lover? Do you meet your spouse's need intimately on their desired schedule? Are you selfless and compromising?
Do you ask yourself, is what I am doing "loving?"