McCarthy's men enjoyed a dream start to the campaign - emerging victorious in their opening two league outings - but things have since went array.
The boss told the club's official website: "Listen, I gave a bad backpass against Dundee United in 1988 and it still annoys me - it really does.
"And I can still see that ball going in against Macedonia when we drew and we went out of the European Championships
"So I hurt for a long, long, long time. But I didn't play badly from 1987 or I didn't defend badly or have a bad time from then on.
"So yes of course they're hurting, but it doesn't have a bearing on you every game you play afterwards."