Why is Qu�bec allowed to separate?

Sorry If I sound a bit thick but I just don't get why what Quebec is doing to the rest of the country is legal! It makes me so mad! The country gives Quebec so much. Canada is basically a slave to Quebec. Their holding us to ransom. Whatever the quebekkers want we HAVE to give to them. I mean how can this be legal? I mean..if they separate Canada loses alot of money, a distinct part of it's culture alot of natural resources, and the maritimes Will be severed from the country. How can this be allowed ? Why are the separatists so selfish ? Can't they see they get everything they want and Canada just keeps pouring into them?