The 26-year-old, who spent 12 years with Saints, became the subject of a protracted and high-profile transfer saga last summer with the Reds making three separate bids before they were successful.
In between those offers there was speculation Lallana had tried to force Southampton's hand by issuing an ultimatum but the player denies that.
A deal for between £23m and £25m was finally agreed but the acrimonious manner of his departure still rankles with fans, who were not assuaged by a full page advert Lallana placed in the local newspaper offering his thanks.
He returns to St Mary's on Sunday where he expects to get a less-than-warm welcome.
"I'm not stupid enough to think the way I left didn't leave a sour taste in a few people's mouths," he told BBC Radio Solent:
"I regret the way I left. I regret bits and pieces of how it happened and it got nasty. It was sad the way it happened.
"What is true is that when I knew of Liverpool's interest and that they had put a bid in, I did say to the club it would be my wish if they could negotiate a fee for me to move on.
"Not for one second did I say I wouldn't play for the club again. I'm man enough to say it was my choice and my decision for me to move on.
"Deep down I hope Saints fans appreciate the times we had at the club together.
"Football is a fickle game - if I do get the jeers and the boos I'm just going to take it as them missing me playing down there because I miss Southampton.
"I miss the fans and I miss the good times we had down there. Of course I do."
Lallana missed the game at Anfield through injury and he admits it will be a strange feeling lining up against his former side this weekend.
"It's still not sunk in that I'm going to be playing against Southampton," he added.
"I think it was a blessing in disguise that I was injured for the first game.
"Even being in the crowd watching that day I just felt really emotional so to have been out there would have been way too soon.
"The rawness of it all has got easier over the past six months.
"I've got huge respect for the club; part of me doesn't even know how I'm going to play. It's all a bit surreal.
"I just have to be professional and play well for Liverpool. I've got too much respect to celebrate (if he scores)."Reuse content