Your car head lights are very important when driving at nights and also in the day time, not just only for you to see but to alert other drivers of your presence on the road. So when replacing a bad bulb you must be aware of how to handle the new bulb or bulbs.
Most headlight bulbs now are filled with halogen and have special coatings on the outside of the glass. If you pick the bulb up by the glass with your fingers, you will leave trace amounts of oil and grease on the glass. When the bulb is used, that area of the glass will get hotter than the rest and it will eventually cause the bulb to crack. When changing headlight bulbs, only hold the metal bulb holder at the base, or make sure you’re wearing rubber surgical / mechanic’s gloves (clean ones) if you’re touching the glass.