Wrong - as many states, including South Carolina (the cause of this latest debate on the issue) clearly stated, it was ALSO about their rights for slaves IN THE NORTH.
As for the economies, as MANY of those states ALSO clearly said, it was ALSO because of the fear of the damage "the north" was doing to their economies - you got that right - but you failed to FINISH THEIR THOUGHTS ON THE MATTER!!! They were afraid of the damage it would cause because of their LOSS OF SLAVE LABOR. They CLEARLY stated that.
Lincoln tried the "long haul" tactic of keeping the union together and then pulling apart slavery from the inside - it didn't work and we had war.
Here are the reasons, IN THEIR OWN WORDS.