Hey.

You know, not long ago I faced more or less the same problem. Felt practicing is just like work (I still do for some things, not all) and there's no enjoyment anymore. Also, for a brief short of time, I thought I'd lost my fire, was not fired up.

What I did, for every moment that I faced this frustration, I never let go of my guitar, and I was talking to myself like: "Listen, this is the thing you've always wanted, you've always dreamed of, DO NOT let go and DO NOT give up. Yes it's hard and at times frustrating, but again, DO NOT give up. Period."

As funny as it might be, it actually worked, with very new song I learned, I became more passionate, I started gradually thinking more about guitar, whenever I'm at work or out with friends I started to actually miss my guitar and at times I just want to be back home playing and such.

I hope this helps, and I really hope you find your fire and muse in something you like.

P.S. For me, when everything else fails, I watch Metallica live on YouTube, and man it fires me up like hell.

Rock on, my friend, and NEVER give up.