"It is never plain sailing through the Pool stages. We dug deep and there was nobody doing anything crazy, nobody was panicking at the end," said O'Connell
"Clermont are an excellent side - very similar to ourselves - and they played very well last week. We are very happy to get out of there with a win.
"We knew they would come out strong like last week. They play with a lot of heart, you could see that today. .
"There was a fear of having a very lonely rest of the season if we lost. We let them gain some very easy yards, even worse than we did last week, and that is something we will have to look at again.
"That game was right up there with the toughest we've ever had in the Heineken Cup. I wish it hadn't been as tight, but we knew it was going to be tough.
"I remember being behind late on against Saracens years ago and Keith Wood scoring. You just have to keep your head up and stay positive
"We found it hard to get territory and get our hands on the ball. When we did have possession we made a few little errors."
O'Connell was involved in a controversial incident in the first half that saw English referee Chris White dismiss his opposite number Jamie Cudmore and give the Munster skipper 10 minute sin the sin bin for fighting.
"I don't really know what happened. I saw him go for Jerry Flannery on the ground and so I stepped in," said O'Connell.
"Before I knew anything he had three punches in on me. These things happen and we have kissed and made up already.
"I have a lot of respect for the way Clermont have played against us in the last few weeks and I'm looking forward to their clash with Sale Sharks.
"This win keeps us in the same position as last week, we still have to win the rest of our Pool games to go through. It is one step further than we were last week."