If someone is coming towards you with oncoming headlights that are bright you should always turn your headlights off the bright setting as soon as you see the oncoming headlights.
The person approaching your vehicle should dim their headlights as well but they don't always do so.
In the event the person doesn't dim their headlights when approaching your vehicle then you need to look down towards the right side of the road to avoid being blinded by the oncoming headlights.
Never try to retaliate against the other driver with turning your high beams on because that can blind the both of you and cause a serious accident.