Cotton picking/independent thumb picking

I've been working on Travis picking for a while now. I can play Dust in the Wind and Don't Think Twice. Recently I discovered Elizabeth Cotton's Freight Train. Man, I want to play this song so bad, but it's so difficult: the independent thump picking and the melody picking. It's kicking my butt. There are times I just want to throw the guitar away because it's so frustrating.

What was your experience like learning to play this song? How did you overcome it? How long did it take you to play the entire song?

I'm still working on the first 8 measures: just the C and G chords. It took me about 2 months to learn Don't Think Twice and a couple of weeks to play Dust in the Wind. I don't know if I could ever learn "Freight Train."

Any help? words of encouragement?