I’m a simple man, strum a little guitar, grew up on Merle Haggard, Roger Miller, etc.. Heard many a great song, but some just eternally stay with me. Some of these songwriters, must be guided by a devine influence, that seems to almost put them in a trance of sorts, in order to put the word together. Words you remember, touch your heart, etc..
I’m not a huge Glen Campbell fan (great guitar player), but when I was around 9 or 10 years old and heard ‘Gentle On My Mind’, the lyrics are incredible, and still take me to a better place.
Written by John Hartford
It's knowing that your door is always open
And your path is free to walk
That makes me tend to leave my sleeping bag
Rolled up and stashed behind your couch
And it's knowing I'm not shackled
By forgotten words and bonds
And the ink stains that are dried upon some line
That keeps you in the back roads by the rivers of my memory
That keeps you ever gentle on my mind
It's not clinging to the rocks and ivy
Planted on their columns now that bind me
Or something that somebody said
Because they thought we fit together walking
It's just knowing that the world will not be cursing or forgiving
When I walk along some railroad track and find
That you're moving on the back roads by the rivers of my memory
And for hours you're just gentle on my mind
Though the wheat fields and the clothes lines
And the junkyards and the highways come between us
And some other woman's cryin' to her mother
'Cause she turned and I was gone
I still might run in silence, tears of joy might stain my face
And the summer sun might burn me 'til I'm blind
But not to where I cannot see you
Walkin' on the back roads, by the rivers flowing gentle on my mind
I dip my cup of soup back
From a gurglin' cracklin' Calderon in some train yard
My beard, a roughening' coal pile
And a dirty hat pulled low across my face, through cupped hands
'Round the tin can, I pretend to hold you to my breast and find
That you're waiting from the back roads by the rivers of my memories
Ever smilin', ever gentle on my mind
Source: Musixmatch
Songwriters: John Hartford

I write and play music.

Writing songs can be very easy, and sometimes difficult.

Overall, writing words is not hard, coming up with subject matter, very simple.

Writing music/melodies is not that hard.

However, matching written music to a "melodic vocal pattern" can be a real challenge at times.

You never know.
One day the song flows out like water down a cliff.
Other days a song stays hidden, frustrates you, makes you want to yell then go for a drive.

...!

I believe Guy Clark kind of summed it up like that.