Over the past few weeks, my typical Friday penance is to abstain from meat.
As I was preparing my breakfast today (Saturday), I realized that yesterday I had forgotten that it was a day of penance.
As I surveyed what I did yesterday, I realized that incidentally, I did not eat meat. ( I was going to, for my dinner, which was a sandwich. Originally I was going to use turkey ham but there was leftover fish in the fridge so I used that instead).
Did I sin? I know that personal sin is voluntary. Unfortunately, that doesn't resolve the question for me. ( Suppose I had eaten meat --* that act would have been a voluntary choice*. As such, the only think I can think of that would disqualify the act from being a sin is that my intention was not to sin (i.e. to defy penance).