Boro are currently a point clear at the top of the Championship table after 30 rounds of matches and are on course to gaining promotion back to the Premier League.
"The day I think everything is done is the day I make a big mistake, so I have to stay calm,” the 41-year-old told BBC Tees.
"I understand the fans and I'm very excited when I go home from work and I think of how the team was when I came and how it is now. But I have to think of the future because nothing is done."
Middlesbrough have been truly brilliant throughout the season and should be considered as one of the top favourites to finish in the top two of the Championship this season.
However, Karanka is taking the right approach by not thinking too far ahead and keeping his feet on the ground.
Boro are unbeaten in 10 games and have one of the best squads in the Championship, but their place in the top two is far from guaranteed.
Derby are arguably the best team in the second tier of English football, and they are just a point behind Middlesbrough in third.
Bournemouth have defied the odds and are level on points with Middlesbrough in second place on goal difference.
Both Derby and Bournemouth will be determined to win automatic promotion to the Premier League, with Ipswich Town, Watford and Brentford not too far behind them in the Championship standings.
Given the competitive nature of the Championship, a single result could have a huge impact on Middlesbrough’s chances of promotion.
Although Boro are on a great run, Karanka is right in asserting that his work is far from done.