Clark is good mates with Coleman from his Fulham days and the pair organised a pre-season friendly between Huddersfield and City back in July.
Speaking to the Huddersfield Examiner, Clark said: "It just shows you how precarious it is.
"When it's someone you know well, and Chris is a very good friend of mine, it makes it tougher.
"But when I got this job a lot of the managers who rang up said not to expect anything other than one day getting the sack.
"They didn't mean it in a bad way, they were just being realistic. "But you have to be optimistic, too. You have to see how long you can stay. Arsene Wenger, Sir Alex Ferguson, David Moyes, they're changing the rules."