That is how Marler reflects on the first 20 minutes of England's second Test against South Africa in Johannesburg during the summer, when the Springboks rampaged into a 22-3 lead.
The pace and power at which South Africa set about England at Ellis Park was a rude awakening for Marler in his second Test. He suddenly knew what international rugby was about.
As England gathered under the posts, they were either going to roll over or fight back. Marler knew the response would determine the true character of Stuart Lancaster's team.
England fought back. They eventually lost 36-27 but built on an improved second-half performance the following week, drawing the third Test 14-14 in Port Elizabeth.
"Standing under the posts after the first 20 minutes of that second Test will stay for me throughout the rest of my career," Marler said.
"I was blowing, South Africa were hammering us and I was thinking 'unless we pull our fingers out we will get 50 points on us here'. That was a moment I thought 'this is a step up'.
"Jannie du Plessis probably gave me a bit of a hiding.
"But it is good to have those moments as reference points. You think 'that is how I want to make someone else feel' because I don't want to experience that again."
And the same applies to England as a team as they prepare for a tough QBE autumn series against Fiji, Australia, South Africa again and then world champions New Zealand.
"That 20-minute period was a turning point in the tightness of the group and the guys coming together as a team and wanting to dig deep for each other in the darkest places," Marler said.
"We were disappointed not to get a win in those three games but the second half of the second Test and the third Test was positive.
"Physically it is a massive step up and you know that if you are not on your game they will just keep coming and keep coming.
"That is the sort of attitude we have in our group. We just want to keep hammering the opposition, keep going, keep going because if they ease off we will take the chance."
Head coach Stuart Lancaster has emphasised to his players that this autumn is "production time", that the lessons learned in South Africa must be put into practice at Twickenham.
If England are to be top seeds at the 2015 Rugby World Cup, they must at least retain their current fourth-place ranking by the end of the series.
Marler's journey towards a potential World Cup place began with a loan spell at Esher and really kicked on when Harlequins addressed their scrummaging issues in December last year.
The introduction of live scrummaging sessions allowed Marler to keep building on some of the tricks of the trade he learned against the "old Teds" in the Championship.
Marler still has an eye-catching hair-cut but he is less of a hot-head on the field nowadays after making deliberate efforts to work on his temperament.
England's forwards coach Graham Rowntree said: "Front-row forwards, more than any other forward on the field, have to experience the coal-face and learn.
"Joe has demonstrated a lot of experience at dealing with pressure, he is playing at a consistent level every week.
"What I see now is a thorough professional and he has quickly become a settled international forward.
"I thought his performances for us in South Africa were very good, against some of the biggest forwards in international rugby, and his performances this season have been consistently very good for Harlequins."
Marler is set to start against Fiji but he is acutely aware that Alex Corbisiero, who is arguably ahead of him in the loosehead pecking order, is on the comeback trail from a knee injury.
Corbisiero will play for London Irish this weekend with the intention of being in consideration for England's clash with Australia next Saturday.
Marler reflects on the competition as healthy. For Rowntree, it is an exciting position to be in, particularly with the 21-year-old Mako Vunipola now also in the mix.
Corbisiero came off the bench at Ellis Park and played a significant role in solidifying England's set-piece but he missed the third Test through injury.
"I'm very happy with what Joe did for us in his last outing, but on top of that, Corbs came on in the second Test and changed things for us, in what was his last game," Rowntree said.
"So we're aware what he can do. We're lucky to have a lot of talent coming through there - Mako has poked his head through this year, that's why he's here.
"Props are getting younger. The fact is, if you're good enough and strong enough, let's get you in."
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