The "Too Hard" song.
 

I have an original song that is (he said modestly) a pretty good song but it's a bear for me to sing and play well. I practice it all the the time, and even nail it once in a while, but it takes a tremendous amount of concentration and I've never played it live. I could change up the guitar part to make it easier, but I think I leave it this way because it makes all my other stuff seem easy by comparison. Any of y'all have something similar?

Yes, I have a song I wrote do not dare to play live. My live playing is reduced two or three levels when playing live, because my mind is not relaxed nor concentrated in playing the guitar. I am usually focusing in a lot of things (i.e. audience, level of noise, sound, etc.). Also, sometimes you are used to playing in ideal conditions (seating, with good lighting, etc) that are rarely replicated live. So you either have to be ultra confortable with a song or you have to tame the level of difficulty you put on it. I have seen some proffessional musicians do the same thing, so it is not a bad thing per se.

I haven't written a whole song that's difficult for me to play myself, but I certainly have composed sections that are a bit tricky to get through cleanly at performance speed. Not sure if that really falls under your description, since I have played them live, although I usually end up wishing I'd played it better.