The astrologer, who was eliminated from BBC One reality show Strictly Come Dancing on Sunday (November 20), appeared on ITV1's breakfast programme Daybreak to talk about the competition.
Grant, who started by talking about losing weight, said: "One of the things that I said when I first went on this big - it wasn't just a diet - if you haven't got positivity, if your state of mind isn't right, and you want to do something, then you're not gonna do it.
"That's why two years ago, the first thing I had to do was to... rediscover my 'bliss'. Where was my bliss? Well, before astrology, it was music, dance [and] drama."
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Grant told presenters Christine Bleakley and John Stapleton about directing a production of A Midsummer Night's Dream at the Stephen Joseph Theatre in Scarborough and appearing as Dusty Springfield in a '60s musical at his local theatre, quipping: "I was so good!"
He also opened up about his experiences as a carer, saying: "Reading the newspapers there about old people in care homes, this is terrible stuff. I was a carer for my grandmother who had dementia, which turned into Alzheimer's.
"So when I lost my grandmother, and my other grandmother - both of whom were very important to me - then I started to spiral downwards. The negativity came, the weight went on, so what I did - to find that bliss that I had lost, to go back to music and singing - was so important to me. And then I could do anything."
Grant said that he believes theatre is an important means of helping people through tough times, explaining: "We must think of theatre as being a therapy for all ages no matter what... if you can get your creative potential out and feel good about what you're doing, you can do anything."
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See a gallery of Russell Grant's Strictly Come Dancing 'best bits' below: