While a brave 1-1 draw in Portugal lifted spirits last month, the same scoreline against Azerbaijan at Windsor Park will have the opposite effect.
Luxembourg also left Belfast with a point in September and O'Neill accepts that a difficult wait now lies in front of him.
"It will be a long three months because we're still looking for our first win," said the former Shamrock Rovers boss.
"If I look back over the seven matches I wouldn't do anything differently: I wouldn't have prepared differently or picked different teams.
"But I have to accept responsibility and I'm happy to do that.
"It's not good enough. We've drawn two games at home that we should have won. These are games we would expect to win but haven't done that.
"I don't think we have lost the momentum (from Portugal) to be honest, but we don't play again until February and we will judge it then."
Northern Ireland had no shortage of opportunities yesterday, with at least half a dozen gilt-edged chances coming and going after Rauf Aliyev's 30-yard screamer gave the visitors a shock fifth-minute lead.
Kyle Lafferty, Craig Cathcart and Chris Baird should all have put the hosts on the scoreboard before record goalscorer David Healy eventually levelled five minutes into added time to register his 36th international goal.
O'Neill declined to criticise his player's profligacy, instead opting to search for positives on a night that was sorely lacking in them.
"I'm hugely disappointed not to win the game because we did everything in our power to do that," he said.
"But I can't fault the players for the effort and they kept going right to the end.
"The players never stopped believing and they got the very least they deserved. They created so many chances and in that it was very similar to the Luxembourg match, even more so than that."
Despite the night's obvious frustration, Healy's first goal in four years gave the home fans something to cheer at the close and O'Neill admitted the fan favourite remains an important figure.
"It's not just about this match and his impact on the pitch, he's just a good player to have around the squad," he said.
"To have Healy around when the younger players come in is fantastic. He knows, realistically, that his impact for us now will be from the bench but it's great to have the option to throw him on.
"I'm delighted for him to get a goal because he's been a fantastic servant."
Azerbaijan manager Berti Vogts reacted philosophically to the late leveller, colourfully suggesting that a higher power than Healy was responsible for the equaliser.
"The God of football is just and he gave Northern Ireland the point they deserved," said the former Germany and Scotland coach.
"Before the game I would have been delighted with a draw, but now I am disappointed not to have won."
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