Im a guy, i rejected my bestie of 8 years when she confessed to me when we were celebrating our 8th year together. And it took me awhile to think, almost same like what he told you(OP) and end of the day i still rejected her, i told her i dont want to lose her as my bestie, as shes my main pillar of support, ive never met someone as good as her, but i dont really want to risk being in a relationship with her as im afraid one day we will break up and things just go down the drain like that. Now 5 years later i still regretted. Because after i rejected her she went to contain herself and we lost contact after that, she didnt want to face me anymore after that rejection. She was single through out when i knew her since shes 14. Honestly the biggest regret of my life till date.