Never be alone with someone of the opposite sex

My boyfriend and my best friend were drunk and were left completely alone. Even though they are two totally different people who would never be attracted to eachother because their personalities clash and they both care about me, they got into a situation neither of them could handle because they were drunk and lack self control.This girl was more like a sister and we were bestfriends for more than a decade and he was the love of my life, and I know they regret it now because her marriage is threatened and he is in rehab for trying to kill himself after he confessed to me. Bottom line- The potential pain it causes to the ones who care about you the most in the world make it not worth it.