Valtteri lined up second on the grid in Montreal, having narrowly missed out on pole position, but struggled to keep up with race leader Sebastian Vettel and had to settle for second.
"I think this was the maximum," the Finn explained. "Saturday was about hundredths of a second, so maybe from pole it could have been different, but from P2 today we maxed out. I'm happy for that, but I'm not happy that we were behind.
"Second place as a driver is not the best place to be - but you know, honestly from today where we started, with the start we had, with the pace we had, there was nothing more possible.
"That's where we are as a team now. Ferrari was better this weekend, Red Bull very close to us, so I think there was nothing we could have done better.
"Our car is just not quick enough, so I don't get too upset being second but no doubt I really want to win. And there have been many occasions this year where it has been pretty close.
"So, for sure, we'll keep pushing on that - but as a team we need to improve, and also for myself, trying to find every single little bit I can."