The former Barcelona and Bayern Munich coach has endured a turbulent start to life at Old Trafford, with United winning just one of their opening five Premier League games.
United have already suffered two top-flight defeats and were hammered 5-3 at newly-promoted Leicester City last Sunday.
An injury crisis has not helped the Dutch coach's preparations so far this season and the squad's fitness problems continue to mount ahead of Saturday's home clash with West Ham, leading Van Gaal to suggest his current job is the hardest he has taken on.
"This is maybe my toughest job," said Van Gaal. "But we have to see in a year.
"As a manager you know already in advance it's a big challenge. This club is in a transition but we will overcome things.
"I don't think my players are robots. They are humans and make errors.
"I am also a manager who always wants to evaluate and discuss things. That's the way I do things. I have done it, this week is no different.
"It's [the Leicester defeat] happened – it’s about overcoming things, it is not a regular occurrence.
"It's very important to get an aura back at Old Trafford. It's very important to win your home games."
United go into the clash with Sam Allardyce's side with a significant list of absentees as no fewer than nine players look set to miss out through injury, while defender Tyler Blackett is suspended after he was shown a red card against Leicester.
Jonny Evans, Phil Jones and Chris Smalling all appear to be out of Saturday's fixture, and Van Gaal acknowledged that he will have to look to the club's famed youth academy for replacements.
He added: "All three of my right-sided centre-halves are out, so I will have to go to the youth education [system] and pick players from there.
"Jonny Evans' bone [in his foot] is bruised a lot and we have to wait and see how it goes. Smalling left yesterday's [Wednesday] session because he had stiff legs. I won't take risks with players - they have to be fit.
"We have nine injuries and one suspension with Blackett. The younger players can have their chance now.
"They are always ready. They are hungry to play the game.
"United's youth education has a level that can provide that. There is a big difference between youth games and the Premier League but in one game you can show yourself."
