Pep Guardiola thanked Liverpool for pushing Manchester City to new heights this season and having claimed the toughest top-flight title of his career warned that his team will return even stronger when they chase a third successive title. City’s 4-1 victory at Brighton ensured they became the first team in a decade to retain the Premier League, holding off a resurgent Liverpool in the process. The champions will attempt to secure an unprecedented domestic treble on Saturday against Watford in the FA Cup final but, having seen their league dominance challenged by Liverpool, plans are afoot to strengthen once more. Guardiola, who has now claimed consecutive championships in La Liga, Bundesliga and the Premier League, won the division by 19 points last season, with that lead trimmed to one this time round. “That was the most difficult title because of the quality of Liverpool and the rivalry we faced all season,” he said. “We made 100 points [last season] and had to make 98 this season to retain it, so it means so much. We have to say congratulations to Liverpool and thanks because they helped us to push and increase our standards. “By doing what we did last season,…