Headlight keep going out any ideas??

[TRICKSIXPA]

Last Night I noticed my headlight was out on the passangerside just the headlight the marker light and the turn signal light are working so I know the ground is hooked up. I replaced it, the plug looked a little black on the one spade. Drove the car this morning both lights working when I left home. The Passanger light was
out by the time I got to work. Any ideas what to check.