Roberto Martinez said Everton paid the price for complacency after the Merseyside club crashed to defeat at Aston Villa last week.
Everton's six-match undefeated streak in the Premier League came to an end against a resurgent Villa outfit on Saturday, as they lost 3-2 away from home.
Martinez conceded his players were handed a reality check following wins against Manchester United, Burnley, Southampton, QPR and Newcastle United, and a draw with Swansea City.
"You do, you do [get carried away]. I think it's only human that you start to feel like you're on top of the world, you feel that you're performing well and that you just need to carry on turning up and getting the results," Martinez told the Liverpool Echo.
"Clearly, in this league, you need to be perfect from game to game.
"I wouldn't say that we dropped our standards at the beginning of the [Villa] game, it was more that we thought we could just turn up and be our normal selves, and that would be enough to get a positive result.
"Clearly that was a reality check. A team like us, we need to be perfect in every game that we go into. It's a shame, because we all know if we'd have had the same level in the first half as we had in the second half, then we would have got the result.
"We are a club that has high standards, every time we are on the football pitch. Now the ball is in our court against Sunderland, to make sure we have a good start and keep it going until the end."
Everton welcome relegation-threatened Sunderland to Goodison Park on Saturday.
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