Xavi's side wrapped up the title after two first-half goals from Robert Lewandowski (34) spurred them to a 4-2 win against city rivals Espanyol on Sunday.
Barcelona were last champions of Spain in the 2018-19 season when they had club greats Lionel Messi (35) and Luis Suarez (36) spearheading their attack.
Yet as the club fell into a deep financial crisis, both had to leave and the team's fortunes declined.
Yet Xavi has guided them back to the summit less than two years after he returned to the club to replace Ronald Koeman (60) in November 2021 and he said wrapping up the title was crucial for their future.
"We are left with a magnificent feeling, more than 10 months of work, of sacrifice. It has been an extraordinary job," Xavi told Movistar Plus.
"For the fans, for the club, winning it was vital for the stability of the project, we must continue on this path.
"This League means that we are doing things very well, this gives us stability, although we still have the unfinished business of European competition."
Barca have failed to get past the last 16 in the Champions League for the last three seasons.
After a glorious run from 2005-19 when the club won four Champions League titles and 10 LaLiga championships, Barcelona have reached the semis of Europe's elite club competition just once since lifting the title in 2014-15.
This season, however, they have enjoyed an outstanding domestic campaign, having beaten bitter rivals Real Madrid in the Spanish Super Cup final and won LaLiga with four games to spare.
Xavi said he had felt the pressure and was glad of the support from his family.
"I thought about my wife, my parents, my brothers and sisters... the staff, who have suffered a lot, those who never fail," Xavi said.
"We are in Spain and here criticism is normal, it happened to me when I was a player, but I am very stubborn and in the end the reward comes when there is good work."
Check out the game summary from Barca's win over their Catalan rivals on Sunday.
