West Ham go to league leaders Manchester City, who cannot afford to drop points against the London side on Sunday with Arsenal two points behind and playing Everton at the same time.
"Football is a strange game. You never know what moments are going to give you the opportunity to win and we have to try to take those opportunities when we can," Moyes told reporters.
"We're not playing to make Manchester City lose the Premier League and we're not playing to make Arsenal win the Premier League.
"We're playing for West Ham and we're trying to win the game for West Ham. We can't finish lower than ninth, which is a really good league position for West Ham in lots of ways."
When asked if they would try to beat City so Declan Rice, who made a 105 million pounds switch to Arsenal last year, could win the league title, Moyes said: "Everybody here loves Declan, everybody will remember him.
"But we're not doing it for Declan, we're doing it for ourselves."
Moyes returned for a second spell at West Ham in 2019 when they hovered above the relegation zone. He is leaving the club by mutual consent when his contract expires at the end of the season.
He guided West Ham to their first trophy in 43 years when they won the Europa Conference League title last season and he took pride in bringing stability to the London side.
"I've been in and out of work at different times but this time I'm happy to be stepping aside. I'm pleased with the work I've done here at West Ham and will leave in good spirits," Moyes said.
"I hope that the people here have enjoyed my company over the period, and I'll keep in touch with them. I've enjoyed my time here, and I'll always look at it fondly.
"I'm very proud to be able to say I helped deliver European football to West Ham. The amount of games we've played has been huge and there are lots of things that show our success."
