The problem with a oil dependent economy is that it's at odds with the "classic" Canadian economy- manufacturing/production and trades that directly benefit from low Canadian dollar. If oil does well, it raises the dollar and stresses one side of the economy; if oil does poorly manufacturing is strengthened but the overall health of economy falters.
It's a very precarious position that the Canadian government has put itself in and could result in some very long-term (on order of decades) problems to fully develop.