:\ That's really fucked up juanif94. But fortunately you're alright!!
I've also been roved about two times with a knife... But not like the motherfuckers really tried to stab me... Just threating me and I always gave my things away. There was also another time, when some dude tried to steal my cellphone with his knife but I didn't let him (yes, I was lucky).
I think the lesson one must learn here is... Never try to confront or play around with an armed person. Some of them don't give a shit about other's life and wouldn't doubt to stab you at any moment if they feel like it. Unfortunate