A mental block or barrier of frustration and anxiety that accompanies one's trouble of forgetting a person they like/love. It occurs when the person likes/loves another person, but due to circumstances, cannot ( or isn't likely to) be with him/her, and realizes this. Thus plunging them into a bout of mixed sad feelings, and when the person tries to forget the one they like/love to ease his/her pain, it is nigh impossible.
A:Hey man, you should stop thinking about her, it's just tearing you up from the inside out.
B: I know I should, but I just can't help it, I just can't tear myself away as easy as I thought I could, it's like there is something keeping me from doing it.
A: Ah, that my friend, is called a cupidian wall. You're hopelessly in love and need some help I assume.