The German midfielder signed for Chicago Fire this week.
He told manutd.com: "If I talk to young players, even here when I speak to youngsters like Jesse, Marcus, [Dutchman] Tim [Fosu-Mensah] and Axel with the first team, I just try to talk to them and help them so they improve as quickly as possible but without losing their own character.
"That's important. I think that everyone has to keep their own individuality and mentality. You should keep it and shouldn't change, just think about some things. If some players take that on, it's good. It's fine if not, though, as it's their own position."