Manager David Moyes has overseen United's a torrid Premier League campaign following Alex Ferguson's departure last year.
The defending champions have lost 10 games to languish in seventh spot, 17 points behind league leaders Liverpool and 10 points adrift of UEFA Champions League qualification.
United will relinquish their crown with five games still to play if they lose to Newcastle United at St James' Park on Saturday.
But for all of this season's disappointments, Smalling says the players will be better for the experience.
"You learn that you can't take what's happened in the previous years for granted," said the England international, who is back in training after being sidelined with a hamstring injury.
"I think this experience will help us make sure we never let this happen again.
"We gave ourselves an uphill task by not starting the season well and, come next season, we will make sure we work harder than ever.
"This club deserves to be at the top and, hopefully, we'll be back there soon enough.
"We definitely want to finish this season on a high. We need to stick together and, if we can get a good run going now and finish strongly, I think we can go into the new season stronger than ever.
"It's a strange feeling for a lot of us to be in the position that we find ourselves in. Even before I joined, and since I’ve been here, we’ve always been competing at the top of the league.
"It hurts. I know how much the fans are hurting as well. I want the supporters to know that we’re always striving to improve.
"Hopefully, we can build up a run between now and the end of the season, as the fans deserve it."
