Well said Mark.
To share my story with you, in my second year of uni i was living with a total bunch of arseholes, and the whole situation depressed me so much i was borderline giving up on guitar. It just wasn't doing anything for me anymore, I had become a mere jukebox, hitting out the same old riffs. So one day, i walked into Virgin cd store, and bought a load of random albums, and one of them (Dark Side of the Moon) totally changed my outlook on life at the time, and i stopped with metal, and started getting more into Floyd, SRV, Jimi and The Beatles.
This to me was a completely different way of playing guitar, and it completely rejuvinated my interest in it.
So maybe that might be all you need? Just a change of music style for a while, then if you want to, go back to metal, or do as i've done, and stay more in bluesy territory. Not that i've given up on metal, i still like some of it, i just realise now that it isn't the only genre of music out there.