Jose Mourinho proclaimed that he is "the Happy One" on his return to Chelsea, adding that he is calmer and a better manager than he has ever been.The 50-year-old, who first managed the Blues between 2004 and 2007, was officially announced as Chelsea's new boss on 3 June."I am the happy one," said Mourinho at a news conference."Calmer? I believe so. I'm in the best moment of my career in terms of knowledge."He added: "I began management in 2000. I thought I knew everything, but after 13 years you realise you know nothing and have to learn every day. My adventures around Europe were fantastic for me, different countries, different cultures, different media. It was fantastic."At 50, I think I am still very young as a manager and I think it was like the beginning of a new period. Do I have a different personality? No, but for sure I have a different approach and perspective."Former Real Madrid boss Mourinho, who replaces Rafael Benitez at Stamford Bridge, has signed a four-year contract and said he wants to stay for the entire term."I hope I can go to the last day of the contract. If the club is happy and the club wants me to stay then I'll be more than happy to stay."When asked whether he was disappointed that neither Manchester United nor Manchester City had approached him about their managerial vacancies, he said: "I am where I want to be - I wouldn't change it for anything."The former Porto and Inter Milan manager helped Chelsea win five major trophies during his first spell at the club - including two Premier League titles, two League cups and an FA Cup. He believes he can emulate that achievement."I want to believe it is possible - I always trust my work," added Mourinho. "In this case I know many people who belong to the club and I know the type of mentality and ambition people have."My career has been built and raised on success. I was able to achieve success and win trophies and leave different types of legacies at every club. I have to believe in that."