Ferguson, who has been in charge at Old Trafford since 1986, confirmed that he currently has no plans to step down and will allow his health to tell him when it is the right time to leave.
The 68-year-old told Riviera Radio: "It's a marvellous club to be involved in.
"The motivation is easy because I've had great players for 25 years and great support. Every morning I go into training and watch these players perform. They do it with great commitment and concentration. It's a joy to see that.
"Age is always a thing you have to be guarded against because with age there are penalties. Health is definitely one. Health determines how long you go on in the club. Touch wood, I'm okay."