Have you ever thought you loved your friend and could be more? That might be possible. You sure have to have a good connection with someone to be a lover but that doesn't mean it will work with your best friend.
The kind of connections have to be special to work with a mate. You can have a great friend of the opposite sex but not have the feeling of love attached to it. You might not get that amazing feeling in your heart, mind, and stomach when you think of the person. You might think about them all the time. You might hang out with them all the time but that sure doesn't mean its going to work out for anything more.
What is it about a lover that makes them just that? What differentiates a best friend from a lover other than not taking the chance?
The physical attraction is a huge part of this. You have to be physically attracted to someone to want to be in a relationship other than a friendship. Both people have to want the other person. Heck you might have a physical attraction to the other person and love hanging out with them but have no want to actually live with them in cohabitants as a team.
You can live with a member of the opposite sex, have sex with them, be attracted but not be compatible on other levels that are wanted and needed. You probably don't have any idea what those things are either. That is why you have to explore life and figure out what you like and don't like and hope you will find the person you want for the rest of your life. That sure doesn't mean you have to not hang out with that person/s anymore. Life is better with more friends of many types.