"There's definitely going to be nerves, and that will never change because there's always that unknown," McCartney said.
"You never know what's going to happen, even if you are on top and in the best shape of your life.
"But as long as you're excited and happy to be there in the mix, they are important."
McCartney is one of the first three of New Zealand's squad of 12 at the worlds who will be in action on Saturday morning, along with sprinter Joseph Millar in the heats of the 100m, and discus thrower Marshall Hall, one of three late additions to the team along with hammer thrower Julia Ratcliffe and javelin thrower Ben Langton Burnell.
The trick with pole vault is there are so many elements involved in a successful leap. Only one aspect needs to go wrong and it can affect the entire routine.
McCartney had trouble at the Stockholm and Oslo Diamond League meets in June with swirly winds in large, open venues. She competed at the Olympic stadium in last year's Diamond League and knows it can present challenges.
However they are balanced by the buzz of the place.
"It can be quite interesting with the wind there. It's a huge stadium and the wind can come in and circle round a bit.
"You've just got to hope for the best on the day.
"The actual stadium is amazing, it can seat so many people and it's so loud when everybody is cheering. It is a pretty special place to compete."
McCartney feels in good shape, having got over a niggling Achilles problem which hindered her Diamond League aspirations.
A 4.75m leap in Rome early in June -- .07s below her personal best set in Auckland early this year - was an encouraging start. Then the injury struck, leaving her to rehab and get ready for London with what she called a ''compromised" preparation.
However her spirits are high, a solid performance, and a victory with plenty of jumps topped by a 4.61m effort, in a meeting in Belgium a week ago, gave her confidence a lift.
There were no injury relapses so she goes into the competition on Saturday morning in good heart.
"There shouldn't be any surprises. We are in a really good space at the moment and in a place I can compete. Even if it's a little bit sore, it's nothing I can't deal with," she said.
McCartney confirmed she will be off a 12-step runup on Saturday, the shortest she's used in a major event, but is on the same poles as Rio, which could be a good omen. She feels "a little bit stronger, a little bit faster, so that helps".
