I’m in love with my best friend!
The Friend Zone - a platonic relationship where one person wishes to enter into love while the other does not. It is generally considered to be an undesirable situation by the love friend. Once the friend zone is established, it is said to be difficult to move beyond that point in a relationship.
Some women don't see their male friends as potential love interests because they fear that deepening their relationship might cause a loss of the romance and mystery or lead to rejection later.