Clark said: "I regarded this game as our game in hand and a chance for us to close the gap on the teams above us in the table.
"We've blown it and it's not the first time it's happened either. I think it's down to a lack of mental toughness.
"I can't complain about the result, though, the only positive was our keeper and our defenders played well to keep a clean sheet.
"But for them doing their jobs properly we would have lost. I thought we were very flat going forward. The front two (Novak and Rhodes) played as poorly as they have done since they became a partnership and that's why I took them off."