After years in the lower leagues, the 32-year-old's fine form for Southampton was rewarded by a first Three Lions call-up last August.
It was an opportunity Lambert grabbed with both hands, scoring the winner in a dream debut against Scotland - a performance that helped see him play a part in every England squad since.
However, with West Ham's Andy Carroll closing in on fitness, the striker's place on the plane to Brazil is far from assured heading into Wednesday's friendly with Denmark.
"Obviously, I still understand it's nowhere near secured," Lambert said of his chances of going to Brazil.
"I've got two months to try and prove my place. It's as simple as that.
"I've always said if I don't make it I'm going to be grateful that I got my chance, and that's still the case now.
"I'm obviously desperate to go and now I've got two months to prove that I'm good enough to go, so that's all I'm trying to focus on now.
"I understand that I've got to do well [this week]. I've got to do well in every training session, any minutes I get. I understand that, it's fine.
"I relish that, to be honest, and that's what I'll be looking forward to. It's going to be great, it's going to be enjoyable."
Lambert has not made any plans for this summer just in case he is included in Roy Hodgson's squad, and nor has Luke Shaw.
Only 18, the uncapped left-back was named in the 30-man squad to face Denmark and makes it a four-strong Saints contingent, joining Adam Lallana, Jay Rodriguez and Lambert.
"I feel like an oldie each time there's a call up," Lambert said.
"I'm made up, I'm absolutely over the moon for the club, and for Luke especially. I think he's had a terrific season and it's fully deserved.
"Whoever he's playing against, whether it's the best right-back in the world, or the best right winger, he'll play his own game and he's confident that he can compete against the best.
"I think his mental strength is one of his main strengths. The way he's handled coming into Southampton, it hasn't bothered him whatsoever. It's frightening.
"Not just him, but all of the kids at Southampton. The way they're prepared, it's in them now. It's full credit to them and the club."