Pogba signed for United for a world-record €105 million fee from Juventus in 2016, but he left the club this summer after six years in which he failed to hit top form for the Premier League side.
The France midfielder scored 39 goals in 226 appearances for United during his second spell at the club and won just two pieces of silverware -- the Europa League and League Cup, both in the 2016-17 season.
Pogba, 29, has now rejoined Juventus on a four-year deal, and in a news conference on his return he addressed his underwhelming time at United.
"I believe in destiny... All the choices I have made in my career, in my life, I've always been very happy with these choices, and that's life," Pogba said.
"Sometimes you make some choices that maybe do not really go as you want. But... I'm very happy [with] the years I spent at Manchester [United] because I grew a lot, I learnt a lot, I became a man when I was there.
"It was not a mistake -- not at all. I was very happy there but you never know what might happen.
"Maybe if I had won something different, maybe also the choices would have been different, but now I'm very happy to be here and I'm glad that I'm back here at Juventus."
Pogba said he had found it hard to adapt to the needs of different managers at United, while he also said positional problems and injuries had taken their toll.
"When you play in a team and you change the coach every year, it's quite difficult to adapt... It's quite difficult to cope with that," Pogba said.
"It's true I also had some injuries, and these probably influenced on my mentality -- the fact that I couldn't play, the fact that I couldn't have the same rhythm that I had before when I was playing 90 minutes every single match.
"There were different elements, different factors all contributed... The coach, the teams, the position on the pitch, so all these factors probably have contributed to block me a little bit in my performance.
"Now that I have left, there is another Paul, it's another Pogba, and I truly hope that I will not get injured again.
"I will be playing in my role, in my position, and so I hope I will be able to do something better than what I have done in the last few years."
Pogba said conversations with Juventus boss Massimiliano Allegri while he was at United had helped convince him to move back to Turin.
"When I was at Manchester [United]... I often talked to him because he was my manager, he was my coach and I've always had a very good relationship with him," Pogba said.
"This last year, it's true that I had a chance to talk to him also before coming here, and now he's here... I spent very beautiful years [at Juventus] and coming back, that I find again Allegri as a coach -- it definitely was the right moment for me with the right person, the right coach."
Pogba won four Serie A titles in a row during his first spell at Juventus, along with two Coppa Italia titles. He scored 34 goals in 178 games for them.
Juventus have not won the Italian title since 2020, however, while this year they finished fourth in the league for a second consecutive year. They were also knocked out of the Champions League round-of-16 for the third campaign in a row.