A number of players still active for the national team featured in all three competitions, including captain and goalkeeper Iker Casillas, midfielders Xavi, Andres Iniesta, Xabi Alonso and Cesc Fabregas and central defender Sergio Ramos.
Del Bosque said in an interview with As newspaper published on Tuesday it was crucial they and their team mates did not let past successes go to their heads at the finals in Brazil starting in June.
"They are players who have won a great deal, almost everything, and they see things through different eyes compared with five or six years ago," Del Bosque said.
"That is the only fear I have," added the 63-year-old former Real Madrid player and coach.
"It is fundamental to be humble, sporting and good lads, nice guys.
"We have to forget about the past and not revel in what we won in the years before.
"We are going to another World Cup, a different one, in a different country and on a different continent, and we have to go there with the same spirit as in South Africa.
"That's the most important thing."
Spain begin the defence of their title against Group B rivals Netherlands, the team they beat 1-0 in the final in 2010, in Salvador on June 13.
They play Chile in Rio De Janeiro on June 18 and Australia in Curitiba five days later.
"Humility is not an empty word," Del Bosque told As.
"When I ask for it, it is because I know it is the path to success.
"Spain has a good national team and is not inferior to anyone but we must be cautious.
"We are the team to beat and there are powerful opponents, mainly the South Americans including Brazil, Colombia, Argentina and Chile.
"Then there are the Europeans, teams like Germany, Holland or Portugal.
"It is not easy and we have to show respect for all our opponents."