Watch the I'm Worried online guitar lesson by Jeff McErlain from Blues Guitar Fakebook: Rhythm Vol. 2
"Worried Life Blues" is an 8 bar blues, and Robben Ford jazzed up the changes by bringing in some classic extensions and substitutions. Michael Landau does a great cover of Robben's version of the tune that I can not recommend enough. A real modern blues rock version where he tears it up. On that note, if you're not familiar with Michael Landau please check him out, he's one of my favorites.