hands up, i'm a lousy songwriter, but we all have to work at most things - everything from sex to fishing> Practice and fool about with a song, learn as much theory as you can stomach so then you can either forget the theory or use it- knowledge is a tool.
Or you can just pinch bits like The Beach Boys nicked Chuck Berry riffs (and so did the Beatles,Ac/Dc ,etc).
I'd start by copying some Chuck Berry licks :D
Try to believe in what you are doing, and if anyone says you ain't doin it right (even if you say that to yourself) don't beleive it.
Accuracy,you say? hmm interesting concept..