Blues found themselves with a mountain to climb after conceding three times in the first half and the Blues boss felt that all of those goals were avoidable.
A much-improved performance after the break saw Blues create a host of chances, but ultimately two goals of their own from Wade Elliott were not enough to take anything away from the fixture.
"I think we got a little bit excited with what happened Friday (when Blues won 4-0 at Palace)," admitted Clark. "We thought we could just turn up and play our football but we forgot that we had to win the battles first because that's how you get the ball. We had so much of the ball at Crystal Palace because we won our battles.
"You win the ball high up the pitch because you do the ugly side of the game. That means players competing, tackling, winning headers and winning second balls. Unfortunately in the first half we didn't have ten outfield players doing that and it's cost us because we've still had the chances to get something from the game.
"We've hit the post three times and we've had other chances that we've missed in the second half so it's a very frustrating day for us. If we'd got three points today we could have gone eighth."
Clark added: "I really feel for the fans because I want to give them proper performances, not just 45 minutes here or there.
"We've just to make sure that when Millwall come here on Saturday we're right back on it again and we're not living off Friday. In this game you've got to move on quickly."