"We thought we'd prepared well, but when we were put under pressure we weren't able to cope."
Hesson said it wasn't one particular part of the group that had to take responsibility for the two batting tumbles at Cape Town and Port Elizabeth.
"I think we all share the load. You certainly can't fault the work ethic. The players have put the work in. This test and the last we just haven't been up to it.
"All of us have to start to challenge whether we're doing the right things and whether we're challenging the players in the right way."
Asked if he had a message for fans at home, Hesson said that while South Africa are ranked No1 "for a reason" New Zealand are ranked No8 "for a reason".
"We're struggling but the players are working extremely hard. They know we're nowhere near where we need to be," he said.
"All we can say is the players are trying their very best and at the moment are being outclassed."