Valtteri Bottas says the "compromises" that Mercedes have had to make with their W08 at some circuits have been a "challenge" for him to drive around.
Although Mercedes are leading both championship races, their W08 hasn't always been the best car on the grid.
As such the Silver Arrows have at times had to make compromises to find the sweet spot, and Bottas says that hasn't always worked for him.
"The only thing I want to do is meet my goals. I've not achieved that lately, which is why I wasn't positive last race," he said.
"The compromises we've made at some circuits to get the car into the window have been a challenge to drive around.
"I’ve had so many answers to my questions as we work out the details with the engineers.
"There's always a positive."
Bottas was his own harshest critic in the wake of disappointing performances in Singapore and Malaysia where he was well and truly beaten by his Mercedes team-mate.
He added: "I’m always honest with myself. I say things how they are.
"It’s been a few difficult races. But Malaysia is now history."