Country music singer-songwriter Billy Joe Shaver canceled his Thursday night show at the Heights Theater in Houston due to illness. Shaver also canceled his Friday show at the Kessler Theater in Dallas.

The Corsicana native is 78, but perhaps with more miles on him than others his age. He was a central figure in the fast-living Outlaw Country music set in the 1970s that made stars of Waylon Jennings and Willie Nelson.

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Never a household name like those two performers, he nevertheless wrote some of the most enduring songs and phrases in country music in that era including "Honky Tonk Heroes," the title track of one of Jennings' best-known albums. Nine of the 10 songs on that album were written by Shaver.

His rough and tumble life started early, when his mother ran off, leaving him to be raised by his grandmother.

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In those 78 years, he's found himself drunk, strung out, involved in numerous fights, and the recipient of two devastating heartbreaks when his wife and son died between 1999 and 2000. A heart attack followed in 2001 necessitating a quadruple bypass surgery.

Through it all Shaver kept writing and recording. He remained stoic and pugnacious through it all. In 2010 he was acquitted for shooting a man outside a Leona bar in 2007.

More on his life story here.

And more on his condition to come.