Fulham finished in 12th in the Premier League after a disappointing end to last season, with Sidwell missing eight games through suspension.
But the 30-year-old believes if Martin Jol's men can maintain their consistency, they will see an improvement next term.
"The season started well, but then we went through a bit of a sticky patch," Sidwell told the club's official website.
"We picked things back up at the start of the year, but then, as we know, we didn't finish the season too well.
"People would probably describe our season as a rollercoaster. We had some ups and downs and we didn't finish as high as we would have liked but there were still positives to be taken.
"On our day we are a very good side, perhaps we just struggled for a bit of consistency at times. We played well in patches and, at the same time, know that we could have played better in other parts of the season."
Fulham have made three new summer signings with Derek Boateng, Fernando Amorebieta and Maarten Stekelenburg agreeing deals.
"It's important to get those new players in early and get the squad nice and settled ahead of the new campaign," added Sidwell.
"I'm looking forward to seeing who else comes in, as last summer we saw the arrival of some very good players."