Highlights - Singapore Grand Prix
Fernando Alonso, winner of the last two grands prix, says the remainder of the season will be his toughest test.
Ferrari's Alonso won in Italy and Singapore to close to within 11 points of Red Bull's championship leader Mark Webber with four races remaining.
But the 29-year-old Spaniard said: "The hard part is still ahead of us.
"Now it starts getting serious, we will have to experience some pain and it is time for everyone to give their all without taking a single backward step."
In one of the most exciting ever finishes to a Formula 1 season, five drivers are still in the hunt for the title.
The McLaren duo of Lewis Hamilton and Jenson Button and Red Bull's Sebastian Vettel are also within 25 points of Webber.
But two-time world champion Alonso's performances in the past two races appear to have given him the momentum going into Sunday's Japanese Grand Prix and the final three races, in South Korea, Brazil and Abu Dhabi.
"I have kept in touch with the team all the time and I know that in Maranello, everyone is delighted with last Sunday's win," said Alonso.
"That's how it should be and I'm happy too, even if I know the hard part is still ahead of us.
"These two consecutive wins have reduced the gap that had built up but we are definitely not leading yet.
"There are still five drivers in the hunt for the title. So many times this year we have seen that the situation can change really quickly, so anything could still happen.
"What is certain is that if any of the five put a foot wrong, then it will be even harder for them.
"I stick with my belief that the key is to always to finish on the podium and then do the maths in Abu Dhabi."
Alonso won the first race of the season in Bahrain in March before drifting down the championship standings as Ferrari struggled to keep pace with Red Bull and McLaren.
But victory in Germany at the end of July reignited his season, paving the way for dominant displays at Monza and Singapore.
"The wins in Monza and Singapore inspire confidence, especially as they came after a difficult season, in which our championship chances have often hung by a thread," Alonso added.
"Winning on two very different types of track confirms that our car is very versatile and so we can tackle the coming races without any fear."