dont worry so much about the 'songwriting' part, get your lyrics down, and the next part isnt playing stuff till u "make up something cool",( or at least for the band im in 6 months of that resulted nothing) the next step after lyrics is to read the lyrics and figure out how you or the person who wrote it wants the song to sound , like the "flow" i guess u could call it. its a billion times easier to do a song like this than the play something till it works. and when u do make up something really cool just fuckin around on bass or guitar write it down, and when your figuring out how the lyrics u wrote want to sound pull em out and see if any of them fit good, ill try and help a fellow jammer out, and remember this is 'my opinion' it might not work for you

"when you fail fall forward instead of back"