Thank you for your question!
As our consciousness changes, we can realize that words such as “differentiate,” are merely intellectual concepts. If this question is responded to you with another intellectual answer to create that “difference,” through a law, through some sort of “never do this, if you don’t want to feel that,” I will be cutting off all possibilities of you knowing by your own experience.
You have an experience of what is attachment. Feel that experience. Observe how it makes you feel. Now, when you feel love or you think or believe to be experiencing love, check if those experiences that you felt in attachment are there. If they are, you know that you have a “mixed” experience.
I can add other words such as: if you feel jealousy, if you feel neediness, if you feel that you cannot be without, if you feel possessive, then that is attachment. I just gave you a wonderful definition. Note that I haven’t described all the “bad” things with their respective labels that you can “feel,” so intellectually, you may think that if you feel “anger” then that is not attachment.
It is anger, you may think; not realizing that attachment is a “bag of bitter candies, of different colors and shapes” thus, if when you feel love, you feel that you are chewing on one of those “bitter candies,” it is time to check yourself and to find out why. Once you find that out, you will see that there are no “fine,” thin lines delimiting love and attachment, but merely “residues,” which need to be clean up in the self.