"I go into this weekend thinking it is going to be my last race. I think that is the best way to be," the 2009 world champion told reporters on Thursday.
"At this moment in time I do not want to be racing in Formula One past this race. I think of this as my last race and hopefully everybody else does as well."
The 36-year-old Briton will be replaced at McLaren by Belgian rookie Stoffel Vandoorne next season but the team have presented the veteran's departure as a year's sabbatical.
That was seen by many as more of an insurance policy in case Spaniard Fernando Alonso decided to walk away at the end of 2017, as well as strengthening McLaren's hand in contract negotiations.
Asked what had changed since September, when the announcement was made, Button said there was nothing in particular.
"I don’t want to go into this race and think it’s not my last. And it is my last," he said. "It is true that I have a contract for 2018 but at this moment in time I don’t want to be racing in 2018.
"The whole idea about having a contract was that in three months’ time, when I’ve eaten myself stupid and am thinking of things to do in the future and maybe feel I need Formula One back in my life...
"But at this moment in time that isn’t the case. So this is my last race and that’s the way I think about it at the moment. But who knows? That could change in six months, eight months, one year."
Button is the most experienced Formula One driver on the grid, and Sunday's race will be the 305th start of a career that started with Williams in 2000. He won the title with Brawn, the team that emerged from the embers of Honda and became Mercedes.
Formula One has been his life's focus since he started out in karting.
"It has been a long journey," he said. "You get to Formula One with many dreams and you aspire to be something. You hope to leave the sport with memories and that is something I definitely do have.
"I raced with two of the teams I dreamt of racing for as a kid, Williams and McLaren, and when I did win the championship it was with a privateer team which I think is also pretty special."