If it gets to the point when you know it’s overheating, remove as much of the load from the grinder as possible and let the grinder run for a while. This will allow the small cooling fan in the motor to flow cool air over the motor. Keep the motor running at speed to ensure the maximum amount of air is being blown or sucked through the motor. DO NOT TURN THE UNIT OFF! Turning the grinder off stops any cooling and allows the heat to ‘Soak’ into the engine which melts components and wires causing your grinder to be permanently damaged. Also, I can recommend you best angle grinder that doesn't overheat, DEWALT DWE402, you can find out more in the article.