The three-time Olympian picked up his sixth Grand Slam title alongside Bethanie Mattek-Sands in the mixed doubles at the US Open.
But in the men's doubles he and Soares failed to progress beyond the quarter-finals in any of the majors, before finishing their season with defeat in the semi-finals of the ATP World Tour Finals on Saturday.
Two years ago the pair were the dominant doubles team in the world with two Grand Slam titles and Murray believes they can get back to that level very quickly in 2019 – with the first Grand Slam in Australia only two months away.
"We were never really contending for No.1 this year," he said.
"For me, you know, I put a lot into my tennis. I want to be the best. I want to finish at No.1 or compete for that. So from that aspect, it was probably a bit of a disappointing season.
"I think we played a lot of really good tennis the second half of the year. Our results showed that.
Jamie Murray of Great Britain and Bruno Soares of Brazil in conversation during the men's doubles third round match against Robin Haase of The Netherlands and Matwe Middelkoop of The Netherlands on Day Eight of the 2018 US Open at the USTA Billie Jean KinGetty Images
"We won a lot of matches. We played some good tennis here, winning three matches against three of the top eight teams in the world. I think that will give us hopefully good momentum going into next year."
Murray and Soares' season ended with a 6-3 4-6 10-4 defeat to Mike Bryan and Jack Sock at the O2 Arena in London and the Scotsman admits it is a frustrating way to bring the curtain down on 2018.
"It was a good-level match, high-level match. A lot of good points being played. We finished the second set strongly, created a lot of opportunities, I felt, going into the tiebreak," he said.
"I thought we had a great chance to win. I'm sure they thought they had a great chance to win, too.
"Two pretty evenly-matched teams, I would say, on paper. It came down to a tiebreak and they played better at the end than we did."