The party must quickly come up with enduring solutions to both its leadership and party structure, he said.
Former leader David Cunliffe stood aside on Tuesday and is now in a leadership battle with Wellington Central MP Grant Robertson.
Tuesday's caucus meeting, at which Mr Cunliffe confirmed his resignation, was difficult, Mr O'Connor said.
Unfortunately, the leadership race came when Labour had already big challenges to complete a comprehensive review of its election defeat.
He agreed with Labour's interim solution – appointing David Parker as temporary leader and Annette King as his deputy.
Mr Parker has called for a "seemly" leadership race, but it's been revealed that Mr Cunliffe's wife Karen Price was behind a Twitter account which anonymously took aim at his rivals and critics.
Mr O'Connor said he was unsure of the meaning of "seemly". "No doubt someone will define it and explain it to me."
Mr Cunliffe has suggested some MPs did not put enough effort into campaigning for the party vote.
Mr O'Connor said only a brave person would try to point fingers in that area.
"In the end the party must present itself as a group of well-focused individuals who represent the values of the party and can connect with the vast majority of New Zealanders. Those people are the candidates."
Under MMP, constituency and list candidates had different job descriptions, he said.
Personally, he had campaigned as strongly for the party as for the electorate.
"But people have the option of two votes these days and some have a bob each way or take two options. That is the reality of MMP."
He acknowledged Labour could expect flak from National when Parliament resumed. He said arrogance was par for the course for National. Most importantly, all opposition MPs should scrutinise government policy, he said.
Former Labour leader David Cunliffe has also been widely accused of arrogance, but Mr O'Connor said the arrogance of Judith Collins, Steven Joyce, and at times John Key, was unmatched.
- By Lee Scanlon of Westport News
