Smalling has struggled for consistency since joining United from Fulham in 2010 but the 25-year-old has flourished under Van Gaal this season, making 22 Premier League appearances.
Smalling, part England's squad to travel to Turin to play Italy in a friendly on Tuesday, gave an assured performance alongside Phil Jones in United's 3-0 win over Liverpool last weekend and is now targeting a successful end to the season.
"The manager has shown a lot of faith in me. Especially over the last couple of months," Smalling told a news conference on Sunday ahead of the Italy game.
"The manager has chosen me and I am enjoying my football. I think he is very honest. He says what you are doing very well and what you can improve. He has real belief in you.
"We have got another eight games, so we will look to finish as strong as we can."
Smalling's contract is set to expire at the end of next season and media reports have linked him with a move away from United, but the former Fulham defender hopes his long-term future is at Old Trafford.
"I have always enjoyed playing for United, especially at the minute," he said. "If I can contribute then I am happy to stay as long as they want me."
Fourth-placed United host Aston Villa in the Premier League on Saturday.
(Reporting by Michael Hann, editing by Ed Osmond)
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