Oneitis
From Ladder Wiki
Oneitis (or "one-itis") is an obsession with one woman. Usually a male that has oneitis for a woman is also her IW. A male with oneitis is convinced that this one woman is special and will 'come around' to him one day in the future. He generally is not interested in anyone else.
It's also important to note that it's really only one-itis when this concern is unfounded in the man for the woman. Such as a man being so dedicated to a woman he is not officially dating or committed to. If there is already a solid relationship in place and the man gives way to thinking she is particularly special or he should be going out of his way for her, that is par for the course for a relationship and that is not considered one-itis. What may be considered one-itis in a relationship is when the relationship is going sour, and it's clear that he should be leaving it, but refuses to believe there are other options. In that situation, it could be dubbed a case of one-itis.
