"A willfully entertained fantasy" IS often a daydream, indeed, it could be an accurate definition of such. And in today's pragmatic, bottom-line, metrics-based world, daydreams should be valued, not chased away. 

Do you not day dream intensely and, at times, incessantly about some one or some thing?  

"A willfully entertained fantasy" is not to be averted or discarded; it is to be cherished. Heck, isn't that LITERALLY what a poem is? Or a love song? Or a love story? Or science fiction?  Or...a day dream? 

Just as its wrong to objectify a woman, it is wrong to objectify a daydream. 

You say I sound new to Catholicism. You sound new to love and romance. (Just as you are wrong, I might be also).  In any case, this might be a great discussion for you and your significant other to have. Without a rule book! And ask her/him what they daydream about you!