It is a powerful profession and it is no wonder so many people want to be songwriters. Some people are born skilled writers. It comes to them like breathing. Others want to write so bad it's killing them, but they can't come up with anything that moves people. The magic, well, I'll probably never understand that part.
Every artist can feel the magic when it happens, some try to explain it.
I heard Arlo Guthrie talking about how he understands songwriting. He used a fishing analogy. I believe the lyric is the most important part of a song. It is primary and fundamental. If the audience doesn't understand what you are saying, then you have not said anything.