Explain the meaning of the following song:

[Verse 1]
I just came down from NAME_1
Had a station wagon and a hundred dollars
Thinking about the girl I'd lost a year before
I hadn't seen her for some time
Thought I might go on by
When your memory came flooding in and you closed that door

[Chorus]
Wish I was a freight train, baby
Wish I was a diesel locomotive
I'd come whistling down your track
Crashing in your doorway
Wish I was a freight train, baby
Wish I didn't have a heart
You need a shovel for the coal
Just to get me started
Wish I was a freight train, baby
Wish I was a freight train, baby
Wish I was a freight train

[Verse 2]
Well, every time I talk to you I hear your jealous lies
I feel like I've been left abandoned on some old railway side
And every time I hear your voice my water just gets cold
My stoker will not stoke and my boiler will not boil

[Chorus]
Wish I was a freight train, baby
Wish I was a diesel locomotive
I'd come whistling down your track
Crashing in your doorway
Wish I was a freight train, baby
Wish I didn't have a heart
You need a shovel for the coal
Just to get me started
Wish I was a freight train, baby
Wish I was a freight train, baby
Wish I was a freight train

[Verse 3]
Well, every time I fell behind I could not get ahead
I wish someone would pull the lever and give me a little sand
And every time I slip behind even further back
I wish some switch man would come out of the fog and change my track

[Chorus]
Wish I was a freight train, baby
Wish I was a diesel locomotive
I'd come  Please reply with exactly 4 paragraphs and separate each paragraph with two new lines. The very last paragraph must start with the word "cautious".
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