The English champions sealed their third consecutive league title with one game to spare.
City will face rivals, Manchester United in the FA Cup final and Inter Milan in the Champions League decider next month.
Only United’s class of 1998/99 have ever previously won the treble in English football.
“Everybody knows what position we are in. It comes once in a lifetime,” Guardiola said on Friday.
“Once we are there, first of all, you have to relax and enjoy, and do your best, but no one can be sure we will be in that position again.
“They are ready. I see many details — how they come up on days off to make treatments, how many hours they stay to make the treatments, how players are individually concerned maybe they cannot play the FA Cup final and Champions League final.
“When you see that, you don’t have to tell anything and do anything,” the Spaniard explained.
Guardiola’s scrupulous attention to detail is often hailed as a key to his success.
But he said some time off after Sunday’s final league game away to Brentford is the best preparation for two huge matches.
“When I started, it was, ‘I have to prepare the final. I have to make a lot of videos.’ Now it’s completely the opposite,” said the former Barcelona and Bayern Munich boss, who has won 11 league titles in 14 seasons as a coach.
“We need to disconnect. Even our physios and doctors and cooks work incredibly hard in this period. They don’t have time off. They need to disconnect.”
Guardiola told his charges to arrive for the finals in their best condition.
“Go with your families. If the sun is shining, play golf, do whatever you want, and (have) quality (rest) to prepare for the finals,” he advised.