The Dutchman arrived at Old Trafford after guiding Netherlands to third place at the 2014 World Cup in Brazil.
Van Gaal was tasked with returning United to the UEFA Champions League after David Moyes' ill-fated spell in charge last season.
The 63-year-old has won seven league titles with four different clubs in three separate countries, but says he will retire whenever his reign at Old Trafford comes to an end.
"This is my last job. For sure," he told The Telegraph.
"I have to pay attention to my kids, my grandchildren but also to my wife. They deserve it. Now I cannot pay that attention.
"I was not at the birthday of my grandson for example. I don't like it.
"My wife wants to quit now already! Five years ago! I'm not married to my job. Of course, I am 24 hours a manager, but I am also 24 hours a father of my children, grandfather of my grandchildren and I am always 24 hours lover of my wife.
"I am married to my profession, more than with her. I see my PA more than my wife."
Van Gaal also praised United captain Wayne Rooney and his team-mate Michael Carrick, who the Dutchman says often come to him to discuss the game.
"He [Rooney] is very open to learn. It's amazing," he said. "I don't know if he speaks with his wife Coleen about football, I don't think so.
"But we have the process of talking here. Most of my players of my selection are open and that's very nice.
"Carrick is more or less a trainer-coach. He is also willing to talk about shapes and systems. That's nice. Rooney also.
"Not every player is very open and then you have to convince him, and then you get a struggle. It works or it doesn't work. Give them time. Also give me time to do it."
