The Mary Poppins legend will celebrate his milestone birthday on December 13 and he's now admitting getting older has plenty of disadvantages because he's outlived most of his best friends and he rarely gets to attend glitzy showbiz events because of his declining health.
He told The Times newspaper: "Though I still do guest spots on TV, and ads and videos, I miss going to the studio every day for a regular series. And every single one of my dearest lifelong friends is gone, which feels just as lonely as it sounds.
"It's frustrating to feel diminished in the world, physically and socially.
"I get invites to events or offers for gigs in New York or Chicago, but that kind of travel takes so much out of me that I have to say no. Almost all of my visiting with folks has to happen at my house."
He went on to explain he has trouble with his mobility, eyesight and hearing, adding: "I am now a stooper, a shuffler and a teeterer. I have feet problems and I go supine as often as is politely possible ...
"My sight is so bad now that origami is out of the question. I have trouble following group conversations and complain frequently about my hearing aids, though I would never refer to them as ear trumpets. I'm not that old."
However, the actor is determined not to become a grumpy old man.
He added: "We all have the capacity for a joyful life. I've made it to 99 in no small part because I have stubbornly refused to give into the bad stuff in life: failures and defeats, personal losses, loneliness and bitterness, the physical and emotional pains of ageing. That stuff is real but I have not let it define me.
"Instead, for the vast majority of my years, I have been in what I can only describe as a full-on bear hug with the experience of living ...
"Boiled down, the things that have kept my life joyful and fulfilling are pretty simple: romance, doing what I love and a whole lot of laughing."
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