Alex Ferguson picked up the League Manager Association's honour on Monday.
At the reception the 71-year-old said he was relieved celebrations to mark his retirement were over.
"It has been overwhelming," he told the awards dinner in London 24 hours after his last match in charge of United, Sunday's 5-5 draw at West Brom.
"The club has been fantastic and congratulations to West Brom with the way they handled yesterday.
In a way I am glad it is all over now - because it has been a very hard week.
"I think (West Brom manager) Steve Clarke should get an award because anyone who scores five against United deserves it."