Toto Wolff insists it would be "dangerous" to assume Mercedes will be favourites at the Belgian GP, but says they have grown stronger as a team after learning "hard lessons" in the first half of the 2017 season.
Mercedes hold a 39-point advantage over Ferrari in the Constructors' Championship ahead of the post-summer return of Formula 1 this weekend, despite the Scuderia's one-two at the previous race in Hungary.
But while the low-downforce Spa track is expected to suit the Silver Arrows' W08 more, Wolff says he is taking nothing granted and also expects Red Bull to be a threat over the next nine races.
"On paper, people will assume that Spa should suit our car because it is a circuit where aerodynamic efficiency is extremely important," the Mercedes executive director said.
"But assumptions are dangerous - we have seen too many times already this season that the form book can be rewritten from one weekend to the next.
"From what we have seen in the first half of the season, the competitive balance will swing one way and another from circuit to circuit. Red Bull will be a threat if they can build on the performance they showed in Hungary.
"So we need to keep our heads down, stay humble regarding our strengths, diligent about our weaknesses and take the season weekend by weekend. The motivation and determination in the factory are greater than ever."
Wolff added that the summer break was the perfect opportunity for Mercedes to take stock of their season so far - with the world champions challenged in the constructors' standings for the first time since winning the 2014 title.
The Silver Arrows have won six races to Ferrari's four, but have been dogged by what Wolff has called a 'diva' of a W08.
"It hasn't been easy sailing," he said. "We have learned hard lessons, grown strong as a group and there are still many areas for us to keep improving.
"It was clear to all of us that 2017 would be a very different season to the three that came before. Then, we had the luxury of a performance advantage to the rest of the field, which meant our two drivers were fighting for the title between themselves.
"For this year, the rules were changed to reset the competitive balance across the field. And it worked. For the first time ever, the champion team has maintained its status as a pacesetter after a big rule change and we are proud that we laid down that marker.
"But that is now history. We have been joined by Ferrari and also Red Bull as the season has developed. This is the new reality we are racing in now and we are open-minded enough to adapt our approach to those new circumstances."
Drivers' title still a priority
While Wolff accepts that the challenge is greater for Mercedes than it has been before, the ambitious targets remain.
Lewis Hamilton trails Sebastian Vettel by 14 points in the Drivers' Championship, but Mercedes are still targeting both titles.
"Our targets remain the same as they were before the first race: to win both championships," Wolff added. "History has shown that the fastest car usually brings you the drivers' title; and the best and most consistent driver pairing wins you the constructors'.
"So the priorities are clear: we must keep bringing performance to the car at every race - and keep racing without mistakes to maximise our performance potential at every track."