why you shouldn't reveal your secrets even to your great friend?

you may find safe revealing your secrets to your best friends, of course, you know them almost as you know yourself & are sure they'll never betray you, there are good chances they are as loyal as you think, but still it's a bad idea to reveal your secrets to them, guess why?

because your great friend has other great friends but you, & those have others, each of them rely blindly on their close friends ...

in the end your secret will be known only from great friends, hundreds of them, & that's before it looses the "secret status", at that point, it doesn't matter a person is a best friend or a worst enemy, he or she will know it anyways ...