The 25-year-old Brazil superstar admitted at a press conference at PSG's Parc des Princes on Friday.
"In Barcelona I had adapted well to the city and the team. I had friends there and it has not been easy," the 25-year-old Brazil superstar admitted at a press conference at PSG's Parc des Princes on Friday.
"It was a tense time, thinking about what I should do in my life. I have left behind a lot of friends, but things go very fast in football."
"I thank all my teammates at Barca for their friendship. I was very happy there for four years but I felt it was time to move on."
Neymar completed his stunning transfer on Thursday when he signed a five-year deal with the French giants after paying 222 million euros ($264 million) to release himself from his contract at Barcelona.
He spent the last four seasons in Catalonia, notably winning two Spanish titles and the Champions League in 2015.
He was part of a lethal front three at Barca alongside Lionel Messi and Luis Suarez, both of whom have taken to social media to wish Neymar well in his new challenge.
There has been a virulent reaction in Barcelona to his decision to leave, which has been compared to Luis Figo's highly controversial switch to Real Madrid in 2000.
But Neymar insisted he did not disrespect the Catalan club in activating his release clause.
"I am sad that supporters -- and I hope it is the minority -- can think that. At no point have I lacked respect towards them or the club."
"All players have the right to want to stay or leave. They are not obliged to stay. If you want to go, when you think it's time to go, I have the right."
The 77-times capped Brazil forward landed at Le Bourget airport to the north-east of Paris on Friday morning before making his way to the Parc des Princes where he was officially unveiled.
"I am very pleased to be able to come to Paris to a big club and a marvellous city," he said.
He joins a club that has been transformed since being taken over by Qatar Sports Investments in 2011. PSG are desperate to win back the French title, lost to Monaco last season, but also win the Champions League for the first time.
Asked why he chose Paris, Neymar said: "For the ambition of the club which is very similar to mine. I want something bigger, a greater challenge. I am here to give my best and help the club win titles."
He is expected to earn 30 million euros net per year throughout his time at PSG, but he rejected claims that his move was driven purely by money.
"I have never been motivated by money. I always follow my heart. I regret that people think that and I thank PSG for believing in my potential," he said.
Neymar also insisted he was fit and ready to make his debut in French football as of Saturday, when PSG host newly promoted Amiens at the Parc des Princes on the opening day of the new Ligue 1 season.
"I always want to play, so I am ready to do so tomorrow. I have trained in pre-season. I stopped for two days, but I am ready, I've seen the pitch and I want to put the PSG shirt on and play."