Think about it: you share the same interests and hobbies. The things you like, and the guys you're interested in, your best friend will also like, or at least won't dislike. And if the guy you're interested in becomes your boyfriend, his personality will likely complement yours, he'll have similar interests, and he'll win your heart. Since that's the case with you, being with your best friend wouldn't be much different.

In fact, whether it's a best friend relationship, a romantic relationship, or a friendship, all relationships are governed by the principles of attraction in interpersonal relationships. Depending on their different needs in interaction, people unconsciously apply these principles of mutual attraction: proximity rate, reciprocity rate, equality rate, induction rate, complementarity rate, and halo attraction rate.
1. Proximity rate
This refers to a relationship where the two people share many commonalities that reduce the spatial and psychological distance between them, making them easily attracted to each other and eventually becoming close friends. The initial reason that makes two people best friends is their closeness to each other.
2. Reciprocity rate
If both parties in a relationship can bring each other benefits and rewards, their mutual attraction will increase. The pursuit of reward and happiness, and the avoidance of punishment and pain, are human nature, and have become subconscious or explicit social behavioral motivations for individuals or groups. These benefits and rewards include the satisfaction of needs such as knowledge, physiology, psychology (liking, respect, trust, praise, recognition), and politics (power, status). The relationship will then progress further. In the case of couples, if their mutual efforts are reciprocated, their love will deepen.
3. Equivalence rate
It means that people generally like those who like them back. This is the psychological mechanism behind the ancient saying, "Those who respect others will always be respected," and "Those who love others will always be loved." If you like someone and they like you, the chances of you becoming friends with them are very high.
4. Induction rate
Attraction is triggered by a natural or man-made environmental factor. In interpersonal interactions, if people are stimulated by a certain trigger that appeals to them, it will arouse their attention and interest in interacting with the other person, thus attracting each other. Imagine if your best friend was heartbroken, and your boyfriend accidentally comforted her and said a few words from her heart. In your absence, it's easy for a man and a woman alone together to develop feelings for each other.
5. Complementarity rate
A strong attraction arises when the personalities, needs, and ways of fulfilling those needs complement each other. Social psychologists Seebau and Kelly believe that a relationship is more likely to continue when both parties benefit from it (complementarity), share a friendly intention (mutual attraction), or discover similar attitudes (similarity). Now think about your relationship with your best friend—is it like this?
6. Halo attraction
This refers to a situation where someone excels in certain abilities, talents, or qualities, or has a high level of social recognition. These positive characteristics act like a halo, creating a sense of attraction and making people feel that all their qualities are appealing, thus encouraging them to approach and interact with them. This kind of attraction is common in life; for example, beautiful women are more likely to find jobs than average-looking women.