It is very common for a person to think about another person while having a deeper relationship with one's partner. Unfortunately, cheating sexually and romantically with others is one of the main reasons for many couples to get drifted away from each other. Even though some people try hard enough to be with their partners, they fail at giving that serious commitment to their partners because of various kinds of pleasures and problems.
Cheating is not only about sleeping with another person or having double standards in dating, if you even think about being with another person when you are right beside your partner, it also comes under the roof of cheating behavioral patterns. On the contrary, no person cheats on one's partner without any proper reason, until and unless that person is either a pervert or a moron who can't control his/her hormones. Every negative aspect in a relationship has some tie-ups with underlying, unobserved, and repetitive practices that ruin a couple's romantic bond. Hence, to get rid of them and to survive one's relationship without falling into the trap of cheating mode, a person must focus on a few feelings which direct him/her/them towards the exploitation of emotional intimacy with one's partner.
Try to notice the base reason for the feelings that make you deflect from your partner even though you are in a good position in your relationship.
See to that whether you are truly happy and satisfied with your partner in every context. And if not, try to analyze the places where you feel something is missing out in your relationship, be it emotional intimacy or physical intimacy.
Try comparing the intensity of the emotion of love you share with your partner in the relationship with the attractions you have for others. Scrutinize and ask yourself whether cheating on your partner is the right move in your relationship.