Cousins will play the final two games of the season against St Kilda and Port Adelaide to end with a career tally of 270 games.
But he said the decision meant ignoring the "selfish reasons" which would have otherwise seen him play on next year with a club he believed was moving toward an era of success.
"The tough part about making this decision is I believe that we, as a foot club, are heading in the right direction," Cousins said.
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"For my own selfish reason I'd love to hang on for another year ... and try to enjoy some of the spoils that are headed our way."
Despite believing he had more games "left in the gun", Cousins said now was unquestionably the right time to end his career.
"I'm happy and content with what I have achieved in footy," he said.
"The thing that I'll miss the most about playing at this club is game day.
"Rocking up in anticipation of the contest and running out that race and looking over my shoulder and walking taller because of the bloke standing next to me.
"Football is an emotional game and that's the way I've played it."
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Tigers coach Damien Hardwick echoed Cousins' mixed feelings.
"From a coaching perspective, we would have liked him to stay another year. Obviously it's very hard to replace players of Ben's calibre," he said.
"From a personal point of view, I can understand what he's feeling."
But the Cousins' story has had low points. Before the Eagles redeemed their one-point loss to the Swans in the 2005 grand final with victory in 2006, Cousins had been stripped of the West Coast captaincy following an incident in which he ran away from a booze bus.
West Coast sacked him in 2007 after his arrest on charges of possessing a prohibited drug.
The charges were dropped, but the AFL deregistered him for 12 months for bringing the game into disrepute.
He praised Richmond for providing him with a second chance in football and in life.
"There were associated risks with picking me up," he said. "Back at the time when I got drafted was a really pivotal time in my life."
He thanked both sets of supporters and said of the support he got from the Tigers and Eagles fans was the highlight of his career.
He also thanked his family, Kevin Sheedy and Gerard Healy who were instrumental in his move to Melbourne and his development on and off the field.
Cousins revealed no definite plans for the future but said he would stay in Melbourne and hopes to remain involved with the Tigers.
He is the subject of a documentary to be screened on Channel 7 later this month, entitled 'Such is Life: The Troubled Times of Ben Cousins'.
