I walk the line

There is a song which is played a lot on Russian radio: Laurent Wolf remix for "I walk the line" by Johnny Cash.

What does "I walk the line" mean in this song?

Quote:

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Originally Posted by Johnny Cash in I Walk the Line

I keep a close watch on this heart of mine
I keep my eyes wide open all the time.
I keep the ends out for the tie that binds
Because you're mine,
I walk the line

I find it very, very easy to be true
I find myself alone when each day is through
Yes, I'll admit I'm a fool for you
Because you're mine,
I walk the line

As sure as night is dark and day is light
I keep you on my mind both day and night
And happiness I've known proves that it's right
Because you're mine,
I walk the line

You've got a way to keep me on your side
You give me cause for love that I can't hide
For you I know I'd even try to turn the tide
Because you're mine,
I walk the line

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http://www.stevenmenke.com/I%20Walk%20T ... 20Page.htm

Johnny with the Temptations (a musical group) outside his door and a new wife at home, wanted the lyrics to say, I’m going to be true to those who believe in me and depend on me to myself and God. Something like I’m still being true, or I’m ( Walking The Line ) .

It means staying honest and behaving honourable.
Not commit any crimes, be unfaithful etc.

Johnny Cash was famous for drinking too much and being unfaithul - so I think, anyway. But he became a Christian and gradually changed his life for the better. As a Christian, his challenge was to "stay on the straight and narrow" an expression that means the same as "walking the line". The song is about the struggle to not behave in an immoral way. He's probably talking about his wife, but it's also possible that he's referring to God/Jesus -- his songs often have a religious side to them.

Sperk and Johanna, thank you! Now the meaning is clear to me.