Stephen Fry worries about becoming "professionally mentally unstable".
The 60-year-old presenter suffers from bipolar disorder and though he is "always prepared" to talk about his struggles, he is concerned that could make his problems worse.
Speaking to Fearne Cotton on her 'Happy Place' podcast, he said: "There was, and still is, and I still feel it occasionally, a danger of becoming sort of professionally mentally unstable, that that's what I am, that's who I am.
"I've always viewed it's not who I am. It's a condition I live with.
"I'm always prepared to talk about it, but there's also a danger, because I do live with this condition.
"I'm not going to kid myself that it's cured, because it isn't, that if I keep picking at the scab, it's not going to be good for me. It's not going to be good for my mental health."
The former 'Q.I.' presenter is thankful his management team and assistant take steps to preserve his mental health and advise him not to push himself too hard.
He said: "I, and certainly the people I work with, my beloved assistant and all the people at my agency, they're very aware of it, and they sense that if I've been asked to do something, and it's a time when I'm just in a cycle, which is not particularly energetic or particularly hopeful, particularly happy, they will...
"I'll say, 'Yes, I'll do it', because I think it's my duty. They'll say, 'No, don't. Don't, or if you do, do it in a month's time'."
The 'Wilde' actor also spoke of how much he missed his "dear friend" Carrie Fisher, who died aged 60 in December 2016, and how she used electroconvulsive therapy to combat her own bipolar disorder.
He said: "I saw her in some states where it really was touch and go, but she would go for electric shock therapy. Of course, she never lost her sense of humour.
"I remember her saying, she said, 'The thing about it is it works for me. It works. It has a few drawbacks. Memory, short-term memory. You lose your short-term memory. The other thing is you lose your short-term memory, losing your short-term memory.' I said, 'Carrie, you're so bad'. She was able to laugh at herself. That's an amazing thing.
"She was a hero, but she also showed that it can bring you down. Her life was shortened by it, there's no question about that."
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