If the pump is operating too far to the left on the curve, this simply means that the pump is delivering high pressure but at a flow rate that is low or non-existent. High pressure inside the pump stresses the impeller unit and thus increases pressure on the motor bearings. In the extreme case, this will cause damage to the pump and motor.
If the flow rate is below the minimum flow rate required for the pump, the pumped medium may also overheat and damage the pump. For this reason, the pump must always be operated inside the lower and upper flow rate bounds. Ideally, the pump should be operated as close as possible to the point of optimal efficiency in order to ensure a long service life and in order to minimize energy consumption.