Sunderland have picked up just two wins in 22 Premier League games and Sunday's 2-1 loss at Norwich left the team just one point above the bottom three.
Gardner, who scored at Carrow Road, admits the team have spoken in length about the reasons for Sunderland's slide towards a relegation fight.
But the midfielder believes the Black Cats cannot afford to feel sorry for themselves and has urged his team-mates to put their words into action before their plight worsens.
He said: "We can't afford to keep talking after games about what we have to do.
"We have to start going out there and doing it. There's no excuses for us anymore. We can't just keep saying things will be fine - we have to make them fine.
"We know we can do it, our second-half performance against Norwich showed that. We know if we play like that, then we'll start winning."
Gardner hopes the side can start their revival with a win over Chelsea at the Stadium of Light on Saturday.
"We are desperate for a win. We need to start pushing on," he said.
"Chelsea will be tough but if we can take that second-half performance into Saturday's game, we can win.
"We're slowly starting to find our form. The problem is we need to find it quickly."