Which gives Friday symbolic significance.
If someone forgets fast or abstain on Friday, do it on Tuesday or Monday. It's not a sin.
Besides, the fish markets need business EVERY DAY OF THE WEEK to stay open.
Abstaining from meat is no chore to me; I much prefer an ahi Tuna to Angus Beef any day of the week.
oops....
Didache - Chapter 8. Fasting and Prayer (the Lord's Prayer). But let not your fasts be with the hypocrites, for they fast on the second and fifth day of the week. Rather, fast on the fourth day and the Preparation (Friday).