Memorized - Yes? No? Maybe?

I was a soloist in a Messiah Sing-along this evening at my church.  I sang "O Thou That Tellest Good Tidings".  I have known this song since high school.  I memorized it back then.  I used it as my college audition.  Then it went on the shelf for awhile.  I brought it out again in 2003 (or thereabouts) for another Messiah.  Then it came out again this year.  I have it memorized.  I've sung it several times in the past week with no mistakes, completely memorized.  But when it came time to sing tonight, I used my music.  Weird, right?  Here's why:

1. All the other soloists were using music.
2. I had a panic moment where I envisioned myself screwing up the song
3. I have this little voice in my head that continually tells me "You don't really have this memorized.  You are going to mess up."
4. With all my years of training and performing, I sometimes flat out don't trust myself. 
5. I'm a chicken.

So, I used my music.  I kind of feel like it was a cop out, but I didn't mess up my song.  I sang it perfectly.  And I was comfortable, because I had the music in front of me.  I really need to learn to trust myself more, but apparently tonight was not the night.  Maybe next year.