I dunno, when I write a song I write what I want to hear, so at first I think its great, but then sometime after when recording I usually doubt it and think they are complete shit. This can be because I hear my favourite bands and lose heart in the face of such great music, or simply because Ive heard my own shit so much when recording and writing I am bored of it. But then I start to like them again when I post them online and get either approval on forums or lots of plays/downloads and comments from fans. But then I start to get bored of them again...
So in that sense, every song I write im unsure of...but it comes in cycles