The dangers of being over promoted?

A tax manager was driving up the motorway on his way to see a client when his senior partner phoned him and told him that he'd been promoted to senior manager. 

The tax manager was so shocked he swerved the car. 

A few minutes later the senior partner phoned the tax manager again to say he'd been promoted even higher and would be made a tax director. 

The manager swerved the car again. 

Then the senior partner told the manager that he was actually being promoted straight to partner. 

The manager was so shocked he drove off the road and went right into a tree. 

The police came and asked him what had happened. He said "I careered off the road"