Out of pitch

Hi What a week it has been. Tuesday for me is band night as I play base trombone for a local band. Now Tuesday was not my night and we were near the end of our 2 hour session and the conductor chose to play A Whiter Shade of Pale. This piece of music I love and the base trombone is rather prominent in the opening bars. I sounded dreadful, I just could not hit the pitch for the opening C which was held for four beats and then change to F for continuing four beats. I was off both and I could just not hit it. We put it down to my lips being tired, which they most likely were. The fact that I had missed quite a few practices and two engagements wouldn’t have helped. But I really felt bad about that. However I resolved to be at next band practice and hope he might choose that tune again. I have been playing for quite a few years so I like to think, well I was not the only one that night. Talk to you soon Alan