Danny N'Guessan's 29th-minute penalty was enough to separate the sides in a scrappy encounter and Cooper saluted his side for their dogged display at the other end of the field.
Cooper said: "We have to get used to the fact that teams are going to put everyone behind the ball to start the game.
"I thought we totally dominated the football for the first 45 minutes, scored a goal, and I think if we got a second one it makes it a lot more comfortable.
"But I asked the players for a clean sheet before the game.
"I said to them that if they got a clean sheet then they would win the game, so they have done that and they won the game.
"There were chances and opportunities around the box which we need to be better at and killing teams off.
"I think it was three weeks ago I was being interviewed sat post-match at Wolves and everyone was buzzing because we played so well but we got beat.
"All I know here is that we got three points, that's the main thing, and the positive thing is we kept a clean sheet."