The former Take That star has achieved record sales of 77 million and regularly sells out arena tours, but when it comes to his greatest achievement in life, Robbie looks to his family rather than his career.
The "Angels" hitmaker has been married to Ayda Field since 2010, and has credited the beauty - with whom he has Teddy, seven, Charlie, five, and 15-month-old Coco - with ending his bachelor days.
He said: "What do I think is my greatest achievement? Monogamy. Yes, it wasn't on the cards. And sobriety I suppose. I could say my kids, but I did very little to achieve the kids - ask Ayda."
Robbie, 45, also admitted he had been concerned that having children with Ayda would "ruin" his life, but has since realised his life is more complete with his brood in the picture.
He added: "I thought these strangers were going to come and ruin the party. And the opposite of that has happened. The universe leaves you these blanks you don't know you need to fill. When the children come these blanks are filled. And you go: oh wow. I am in a different level. I have achieved level 'family'.
"If you are surrounded by love then you will be love. And if you feel loved then you are whole. That is what I have learned from therapy."
But despite being sober and leaving his partying days behind him, the 'Let Me Entertain You' singer has confessed he still battles with his demons on a daily basis.
Speaking to Australia's "A Current Affair" show, he said: "It doesn't go away. I don't think you ever stop feeling odd."