The 73-year-old is looking to secure a sixth win in seven games when he and Shaun Maloney end an interim spell at the helm of the Glasgow giants away to Hibernian in the Scottish Premiership on Sunday.
O'Neill had not managed since a brief spell with Nottingham Forest in 2019.
But the Northern Irishman, who enjoyed great success during his first spell as Celtic boss from 2000-2005, returned to Parkhead last month after manager Brendan Rodgers resigned following a breakdown in his relations with majority shareholder Dermot Desmond.
Wilfried Nancy has been tipped to take over on a full-time basis at Celtic, with the Frenchman set to inherit a side already in the Scottish League Cup final and looking to make progress in the Europa League.
"During my time when I wasn't managing, I always thought I could manage," O'Neill told reporters ahead of Sunday's match at Easter Road.
"And when I saw some teams I thought I could do equally as badly as somebody else....
"But the appetite, it's honestly, it's always there. And in my last days on Earth, I'll still be thinking, 'Yeah, I'll be able to do that'.
"But this has been an opportunity given to me, and a man (Desmond) handed it to me who handed me the opportunity 25 years ago to manage this football club."
O'Neill added he would have been "dubious" about taking charge of any other club on an interim basis, but said that "the call to manage Celtic again was really, really too great".