In an interview with the Telegraph the Harlequins prop, who is yet to start a test for England, admitted several leading players talked to him about the need to curb his hot headed ways after a match between Harlequins and Wasps last year.
"I was fuming that we were playing so badly and I could've probably been sent off about two or three times in that game," Sinckler said.
"James Horwill and Adam Jones sat me down and took it upon themselves to tell me on that Monday after 'look you've got to stop it because it's all about you.'
"That's how it comes across, it's all about me, and it's always me starting the fights and costing the team, and it's bigger than yourself so I need to sit back and think if Adam Jones - 95 caps for Wales - and James Horwill - 60-70 caps, Australia captain, led them to a World Cup in New Zealand - those guys have gone out of their way to speak to me and they didn't have to and they just said you've got a lot of talent but if you don't sort your image out and sort yourself out."
Harlequins and Lions front-row colleague Joe Marler was another to suggest likewise.
"Joe sat me down and said 'you've got to stop it'," Sinckler said.
"I'm just grateful those guys were happy to talk to me because that flicked a switch there and then and I was lucky enough to go on tour to Australia with England that summer, Eddie [Jones] took a chance on me as I'd only started two or three games for Harlequins that summer and yeah, that conversation with James Horwill and Adam Jones flicked the switch and always having Joe tell me on the pitch - as you guys in the English media usually see - always having a go at me and telling me to shut up and stuff.
"It's an ongoing process for me, I want to be physical, I want to play on the edge and in people's faces but in the right way, and not to the detriment of the team. That conversation with James Horwill and Adam Jones put things in perspective for me."
Sinckler also said he had discussed this issue with Harlequins psychologist, Pieter Kruger, and Jeremy Snape with England. "After that conversation I've sat down with them and spoken to them. It's a part of maturing as well.
"I'm still growing, still becoming a man, learning from my mistakes. Hopefully I just keep learning and the biggest thing is just the team, you've got to put yourself before the team."
After this latest incident, it appears Sinckler still has plenty of work ahead of him.