Q: My front passenger headlight keeps going out

The first thing you want to do is make sure the bulb is actually burned out, that is the filament tests "open", as opposed to a situation where you have a good bulb but a bad terminal connection. You’ll need an ohmmeter to test the bulb or YourMechanic can do it for you. If the filament has truly burned out, as confirmed by testing, and it burned out within days of installation, then it is not likely that mere condensation on the inside of the lens is the cause. If the bulb is sitting in liquid water and/or you have touched the bulb glass, that can cause problems though. Touching the bulb glass can cause it to shatter once hot.

Assuming there is no excessive vibration, that is assuming the bulb is not being banged around, repetitive premature burn-out of the FILAMENT in a bulb is due to consistently high voltage on the circuit and/or voltage excursions. If that fault exists an electrical diagnostic will pick it up and thus that is the recommended diagnostic in your circumstance. If the voltage supplying the lamp is confirmed "high", the faulty component will be identified during the diagnostic and the necessary repair(s) estimated for you.