The 24-year-old moved to Old Trafford from Ajax last summer for £40 million but only started four Premier League games last season and was an unused substitute in the Europa League defeat to Villarreal.
The Netherlands international has failed to play a single minute in the opening three league matches this campaign and said it has affected his confidence.
“I think the start was good, my first game I scored [against Crystal Palace] and I think I did well but after that it’s difficult if you’re not really in the team and if you’re waiting for your chance,” he told Rio Ferdinand’s Vibe with Five podcast.
“That’s not easy if you’re not playing, also not for the confidence. But, OK, the first year you come from a different competition and it’s normal that you need to have time to adapt and everything but of course you are not happy. I want to play. That is clear.
“That’s so hard, also mentally. It’s so difficult, the only thing you can do is train really hard every day, I try to improve and just wait for your chance. It’s the only thing I can do. If the moment is there I have to be ready.
“If you’re not playing you could sit there and just be angry but that’s not the key to coming into the team. You have to do everything and also help them when you can. Of course sometimes you’re angry, every player gets that, but you’re not going to show them if you don’t train hard any more, then you give the manager a reason to play without you. I think that’s the key, always be positive.”
Although Van de Beek stayed at the club this summer amid speculation around his future, sources have told ESPN that United are keen to add another midfielder to the squad next season and want to sign West Ham United‘s Declan Rice.
Van de Beek also said he has spoken with United manager Ole Gunnar Solskjaer and he is confident of enjoying more minutes on the pitch this season.
“I need to trust him,” Van de Beek added. “If he doesn’t need me I think he will let me go. I think he has plans for me, I just need to work hard and I hope one day I can show the people what I can do.
“I speak with the manager about it and the club. They were clear they want me to stay here. The manager was really positive about me and he said: ‘I need you and I want to keep you here because what I see every day in training now is a different Donny.'”