Increasing desire for one person/decreasing for another

I have been married for almost 20 years and for the past several, I have felt like I no longer love him. In the meantime, I have fallen in love with someone else (who is not available). I know I need to separate myself from that person in order to be able to focus on my marriage, but I am struggling.
Is it really possible to increase my desire for my husband and decrease desire for the other man? What if this other man is really MY PERSON?