The Astana rider won his fourth stage of this year's Tour in the challenging 145.5km route from Pau to Hautacam on Thursday.
Nibali now has a lead of seven minutes and 10 seconds over Thibaut Pinot in the general classification, and with just three stages remaining the Italian has a seemingly unassailable lead.
"I feel I am in control of the Tour," he said. "It is a big gap. More than seven minutes means I am feeling confident for the last few stages and I am also feeling a lot calmer.
"I will try and have a quiet stage tomorrow, and then we move into the time trial [on Saturday], where I will try to do as well as I can.
"It's normal to control the race when we lead the overall classification. I've done what I had to do with the experience I had from winning the Giro [d'Italia] and the Vuelta [a Espana], from making the podium at the Giro, the Tour and the Vuelta, from riding aggressively in the classics even when I wasn't in a great shape.
"I came to the Tour with a good preparation and a good team."
Movistar's Alejandro Valverde lost his grip on second place after struggling on the final climb and is now 15 seconds adrift of second-placed Pinot, in fourth.
The Spaniard admits to feeling the physical effects of the Tour but refuses to give up on second spot.
"I must now see whether I recover or not," he commented. "I was at my limits today, for sure, but like everybody else, we are going to have to do with the strengths we have left and go ahead.
"I'm really, really tired, but for the time trial everything depends on the form of the day. If I have good legs, I can take the second place back.
"It is not a dramatic day today. Today, I just had to suffer and hang in there - that is what I did, to finish with as much dignity as possible."