Many people experience conflicted romantic infidelity, meaning they're in love with both their primary partner and with a new partner. There is a misconception that you cannot be in love with two people at the same time. Of course you can. They're very different types of feelings.
A lot of people feel attachment type of love toward their primary partner, and then limerence, lustful type of love toward the new partner. This, of course, leads to a great conflict between this attachment, warm fuzzy feeling toward one person and this very lustful, passionate feeling toward the new partner.
Conflicted romantic infidelity is a very tough situation to be in, because feelings one experiences toward both people are very real and very strong. One way to deal with it, of course, is to evaluate your primary relationship to see what was missing in the relationship that led you to seek out another person,
Realizing that the limerent, passionate, lustful feeling toward the new partner will pass is also very important. That kind of passionate feeling usually does not last more than 18 to 36 months. That is driven by dopamine hormone, which usually wears off.
When someone experiences conflicted romantic infidelity, it is because there are two conflicting hormones or neurotransmitters that are driving their behavior. They feel attachment type love toward their primary partner. That attachment love is driven by oxytocin, a warm, fuzzy hormone that is excreted when we feel close and intimate with someone.
In the same time, they're experience passionate, limerent, lustful type of feeling toward the new partner. That feeling is driven by dopamine, a hormone off motivation and desire. When those two hormones conflict, it's a very difficult situation to be in, because you have to choose between a feeling of security and closeness and feeling of passion and desire.