Speaking to the CT, Clingan said: "Supporters will look at some games and think 'that's a guaranteed three points' but it's never as easy as that.
"I know from Northern Ireland - when we got a draw against Italy, people thought we were looking at a four or five goal win against the Faroe Islands, but's not like that any more.
"Every game is tough and you always have to be properly prepared, mentally and physically.
"We can take a lot of positives out of the Cardiff game on Tuesday night and so we can put it to the back of our minds now and hopefully pick up some points against Barnsley, because six points from nine for the week would be a good effort."