The Southampton striker has kept his place in Roy Hodgson's squad for the final World Cup 2014 qualifying Group H fixtures against Montenegro and Poland.
Lambert has netted two goals in three games for his country since being called up at the start of the season, and is still in dreamland about getting his chance at international level at the age of 31.
"If I don't get to play for England again, I'll still be happy with what I have achieved so far," he told the Daily Mirror. "This is already the best season of my career.
"Obviously, I don't need to tell you how determined I am not to let it end now. But if it did, then I am more than happy with the way it has gone."
On the prospect of flying to Brazil next summer, he added: "There's a lot of things that have got to happen between now and then.
"I'll just keep working hard. I've never taken anything for granted. And if that chance does come then, yes, I will take it."
Lambert's rise from the lower leagues to the world stage has been well documented and he has urged those reaching for the stars to keep striving.
"I'm hoping to inspire other people to not give up because if you are good enough, you will get to where you want to go," said Lambert.
"You never know what could happen in a year, two years. It can change. It's hard at the moment because the Premier League is not investing a lot in the lower leagues.
"Clubs would rather bring in a foreign player than go lower, so it's not easy. But it's not impossible, and so you can't give up."
Lambert has netted twice in the Premier League so far this season having netted 15 goals in the last campaign, and with Saints riding high in fourth, he is keen to try and sharpen his game.
"Personally, I feel I can improve even further," he added.
"Being around the England set-up will bring more out of me. I might be 31 but there is so much still for me to learn from the manager and the players.
"To go to Ukraine as we did, in that atmosphere, and get a point against the players they've got, was a great achievement.
"We were desperate to get into a position where we were top, and now it is in our hands."