The Scot had written off competing in the Games and had even booked a holiday in the West Country to coincide with the Olympics – which he will not cancel until after British Cycling confirm that he is in their team for London 2012.
Millar is expected to be on the long list for the men's road race team, which is to be announced today, after missing the Beijing Games in 2008 and Athens in 2004 due to the British Olympic Association's (BOA) lifetime ban for any athlete who is found guilty of a doping offence.
The 35-year-old served a two-year ban in 2004 after admitting taking the blood-boosting agent EPO, and since then has become a leading campaigner against doping and an adviser to the World Anti-Doping Agency.
The BOA's defeat last month in the Court of Arbitration for Sport (CAS) over their lifetime ban means Millar, like sprinter Dwain Chambers, is now able to compete in London 12 years after his first Olympics.
Millar said: "This is not the easy path for me. I had written off the Olympics a long time ago and had even booked a holiday for after the Tour de France. To decide to go to the Olympics is to now regurgitate everything and deal possibly with negative reactions and interviews about the past; and to go back to living in the past is not something I want to do, I want to look forward.
"Digging up the past and having to justify myself and deal with the media, it would have been much easier for me simply to not go – then all I would probably have got was a positive reaction from martyring myself.
"But the biggest regret I could have is deciding to take the easy option, take my holiday, watch the road race on TV and see the British team and see what a stupid, selfish decision I had taken."
Millar is not expecting to emerge from London with any medal around his neck – the team nature of the road race event means his role will be to help put Mark Cavendish in a position to sprint for gold at the finish. It is possible, however, that he could also be the second time-trial rider alongside Bradley Wiggins, in which case he could compete for a medal.
Millar insisted: "I would not be going there anticipating a medal. We have an objective and that's helping Mark to win. It's unlike many other Olympic events in that sense and I think that is even more confusing for people to understand. I will be going to support Mark and the British cycling team.
"I don't want to have any regrets about letting the team down because I'm worried about a backlash and what it would do to me, which was the only reason for not putting myself forward."
Millar added that he would fully understand if British Cycling's performance director Dave Brailsford decided his inclusion would unsettle the team.