The 46-year-old singer was struck down with coronavirus symptoms while in quarantine after a cancelled gig in Australia, and Robbie has now admitted he was genuinely fearful for his life.
He shared: "When I landed back in Los Angeles it was unusually cloudy and grey, and what with everything going on it did feel very apocalyptic.
"I was in quarantine in an Airbnb down the road from my family and started worrying about food, about my medication running out ... and was just very fearful for a couple of days.
"Then I could feel my body was getting lethargic and tired and heavy and I convinced myself I'd got coronavirus."
Robbie subsequently decided to pray for his health and that of his family.
And according to the 'Angels' hitmaker, he managed to overcome his symptoms remarkably quickly.
Robbie - who has been married to actress Ayda Field since 2010 - told The Sun on Sunday newspaper: "I never normally do it but I got down on my knees and prayed. I thought about my wife and family.
"Within 30 seconds I had lifted my vibration and was in love. And you know what? The symptoms went away and the fear went away.
"I've now safeguarded myself against lower energies, against feelings of worthlessness. I have to do this because I am a depressive.
"If I don't keep myself safe then it's not a pleasant place to be. Please excuse my whimsy when I say isolation is easy - what I mean is that I am doing estimable things for myself where I raise my frequency and I don't give in to the temptations of those negative thoughts and feelings."