City are fourth in the league following defeat at Chelsea on Wednesday, all but ending hopes of a league title in the Catalan's debut campaign in England.
"In future I will be better - definitely," said the former Barcelona and Bayern Munich coach.
"This season has been a massive lesson for me."
He added: "We have a lot of beautiful things to fight for and to qualify for the Champions League will be a huge success. But we have to be honest with ourselves. We were not good enough to compete for the Premier League [title]."
Defeat at Stamford Bridge left City just four points ahead of Arsenal and Manchester United, both of whom have a game in hand.
With the FA Cup being City's only realistic chance of winning a trophy this term, it is likely to be the worst season of Guardiola's managerial career.
The 46-year-old has never gone a single season without winning a trophy - he has won the title in six out of seven attempts and his sides have always reached the last four of the Champions League.
Guardiola has also responded to questions about a row between City and Chelsea coaching staff at Stamford Bridge following the defeat on Wednesday night.
There have been conflicting claims about the precise nature of the row, but stewards were needed to calm the situation down after Chelsea's 2-1 win.
The incident centred around a disagreement between Chelsea fitness coach Paolo Bertelli and Manchester City masseur Mark Sertori, both of whom speak Italian, as the Premier League leaders celebrated their victory.
Guardiola said: "We are so polite in our defeats and we are so polite when we win. When we win, normally we celebrate a little bit, then we go to the locker room.
Chelsea manager Antonio Conte was not involved and has played the incident down.
He said: "Respect is the most important thing in football."
Manchester City boss Pep Guardiola says his first season in the Premier League has not been good enough but promised "in the future I will be better".