"Last year I said I was going to quit, but later I changed it and I said I would take a sabbatical," Van Gaal told Algemeen Dagblad after being handed a lifetime award by the Dutch government on Monday night.
"Now I believe I will not return any more. So many things have happened in my family recently, so that really was a wake up call and it put everything into perspective."
Van Gaal is referring to the loss of his son-in-law, who died recently, months after the Dutchman's Man Utd exit in May as he was replaced by former understudy Jose Mourinho despite an FA Cup final victory.
After a relatively unremarkable playing career, Van Gaal became Ajax head coach in 1992 following six years on the sidelines in the Eredivisie.
He won league titles with Ajax in 1994, 1995 and 1996 and - even more impressively - triumphed in the Champions League during that period of phenomenal success.
Van Gaal left for Barcelona in 1997, where he won two Primera Division titles, one Copa del Rey crown, and the UEFA Super Cup.
He began his first spell as Netherlands in 2000 but infamously failed to reach World Cup 2002 despite a talented team including Edgar Davids, Marc Overmars and Phillip Cocu.
An ill-fated, six-month return to Barcelona was followed by a brief stint as Ajax technical director, before spending four years in charge of Dutch club AZ.
Van Gaal took Bayern Munich to the Champions League final in his first year in charge, securing a domestic double in the Bundesliga and DFB-Pokal, but in 2010-11 his team were a shadow of themselves and he was sacked towards the end of the season.
His second spell in charge at Netherlands was a stark contrast to his first attempt at national management, as the Oranje reached the World Cup 2014 semi-finals.
Van Gaal finished his career with two years in charge at Manchester United. He was a controversial figure as many supporters didn't feel the club progressed with the Dutchman at the helm, before his former understudy at Barcelona, Jose Mourinho, replaced him in May 2016 despite FA Cup final victory.