Wordless Lessons

If you close your mind to ideas and experiences that you think are bad for you then you are making yourself deaf to the voice of experience.
This does not mean you should stick a knife in your hand so you can “hear” a lesson. But it does mean that if you ignore or condemn the man who puts a knife in his hand (or someone's back for that matter) then you will not “hear” the lesson that this experience was meant to convey.
The lesson you miss is not meant for words. If it were, then no stabbing would have been necessary, you could just be told. So no one can simply tell you what the lesson is that you will miss. You must learn for yourself. And the lesson will be repeated over and over until you do. So if you have to stick a knife in your hand in order to understand, then maybe you should.