[Chrislong]

High temperatures reduce the magnetic force of the rotor, which then reduces performance AND causes further heat, its a vicious circle. The magnetic force will return when cooled, but it does reduce it overall if you keep doing it - and then it'll always run hot and slower than it should.

Don't use a fan on the motor, it'll just make it seem cooler on the outside when its still hot inside. Fans are only effective on motors which are running right to begin with, the additional cooling will aid performance (cold magnets are most effective).