ode to writing songs...

Zdravstvuite!
Ok so this isn't really an ode. I'm not sure I know what an ode is actually. Anyhow, I would like to know.. What do you think is the hardest part about writing songs? The lyrics..or the melody? or both? Maybe you just can't do it at all...lol Some got it and some don't.. :}
I think personally for me it depends on what I start with. Sometimes I hear a melody in my head, but I can't for the life of me think of words to go with it. Other times I have a thought caught in my head and it turns into a song..but then I can't think of a melody to do it justice. It's a vicious cycle.. lol Songwriting is a mysterious art, Not for the faint of heart... :P
Sometimes you have one phrase and you knows where you want to go with it...but you can't think of how to tie it together.
Take this phrase for instance:
"Midnight Kings, in Moth-eaten Robes, the feast is rotting away.." This is an idea I had for a song about how things in life don't last forever, no matter how hard you try. It's a complete thought, but it isn't easy to elaborate on.
So anyway. If you are anywhere out there listening..give me some feedback! What helps you when you write a song? What is hardest for you? Any Brainstorming tips?
ttyl,
Becca.