The veteran star hung up his boots this week having played at every level in the English professional ranks.
Lambert enjoyed great success at Southampton and bagged 106 goals in 207 appearances.
He secured a high-profile switch to Anfield in 2014 but struggled to make an impact.
After just three Premier League goals for the Reds he was moved on to West Brom.
Lambert says his lack of match action at Liverpool affected him mentally.
"I was getting well paid but I never started playing football for the money,” he told the Daily Mail.
“And when I decided to go to Liverpool I sacrificed a regular first-team place and that was when I started to fall out of love with it.
“I never should have accepted being on the bench, even though Brendan Rodgers had made it clear to me I would be back-up for Suarez and Sturridge.
“I was never as quick or as technically good as the best players, but in my own head, when it came to actually playing, I could convince myself I was the best.
“But when I joined up with England I felt lucky to be there, and it was the same at Liverpool.
“And when I look back now I realise I lost something mentally as a player, by allowing that to happen.”
