I thought you were ( i know you are ) much more square-logic than that.
So a lot of 50 year olds beat you, So what? Who are they? Do you know what they did to get to that race? Do you know if it was a couch potato that closed his PS3 to come and beat your slow ass, or maybe it was Carl Lewis (53) taking a meet for fun? Do you think you can beat MJ in a 1-on-1 today? Dr.J. can still dunk at 65 btw.
Where am i going with this: Do other peoples performances matter? Well in general yes, but a track meet, your very first track meet, they don't.
You are at a given body and conditioning state. You sprint and time yourself daily. You are injured currently and unable to strength train for a long time now.
So according to your general state and latest splits, should you expect something better than 13.3s? And does 13.3 change its own substance and significance when it is in a results page between some 50yo guys and 12.xx girls?
Didn't think so