Hook replaced Rhys Priestland in the Wales starting lineup for their World Cup semi-final against the French last weekend.
However, the 26-year-old missed two penalties and was replaced after 45 minutes of the match as Wales went down 9-8.
"You have to draw a line under it and get it right this week," said Hook.
"You have setbacks in your career and I'm not going to let it disrupt me this week, I'm just going out there to relax and enjoy the occasion, I'm not going to worry about too much else.
"I'm delighted to get the opportunity to put it behind me and get on with what should be a huge challenge if we are to come third in this tournament and finish on a high."
If Wales beat Australia in the third-place play-off in Auckland they will match their best ever performance in a World Cup.