Blues dominated the first 45 minutes against the high-flying Bluebirds, but fell behind just before the break when the ball fell kindly to Joe Mason to put it into the back of an empty net.
Clark was naturally disappointed after seeing his side give such a good account of themselves.
“Without a doubt I think we deserved something,” said the Blues boss.
“The goal we gave away was very fortunate. I’ve just seen it. Jack saves it and it then hits him on the back of the head and then hits him on the heel and rolls straight to Joe Mason who is there to tap it in. That was the bad luck we got with the goal but we didn’t deserve to be losing it anyway.
“We played some excellent football and it’s horrible because we’re in the business of picking up points. The performance out there of all the players individually and collectively was very good against a team that is probably going to get promoted.
“The only point I would make to the players is certainly in the second half - we should have pulled the trigger more. We had opportunities and we tried to walk it into the goal or were looking for the perfect shooting opportunity, whereas sometimes when you’ve got lots of bodies in the box yourself and there are lots of Cardiff City defenders you hit a shot and it might not be the best shot but you might get a deflection and it goes in. That would be my only little nit-pick at the players because they’ve had a terrific go at them.”
Clark concluded: "We just need to keep soldiering on and go for it and keep our spirits high and be positive. Hopefully when you do that and keep working as hard as you can and give it your best things will start to change for you."