Felix joined Atletico from Benfica for a club record fee of 126 million euros in 2019 but has struggled to realise his potential, scoring 25 goals in three-and-a-half seasons before joining Chelsea on January until the end of the campaign.
The Portugal forward was sent off on his Premier League debut last month against Fulham, earning a three-match ban, but is due to return to action on Saturday against West Ham United.
"I had been looking for a change of scenery for some time because it was difficult for me to get used to the way of playing," Felix told Spanish newspaper AS in an interview published on Friday.
"I left because my head was full of the fact I was trying and not being able to. It had to be in this transfer window and I think it has been good for Atletico and for me too."
Felix's dribbling and passing ability encouraged Chelsea to pay a reported 9 million pounds to sign him on loan but his skills have not always dovetailed with Simeone, whose Atletico side tend to prioritise defending over attacking.
Felix stopped short of openly criticising the Argentine coach but hinted the pair have not always seen eye-to-eye with each other.
"He is a very good coach. He has his way of understanding and seeing football that others don't have. That's good for some and bad for others. It depends on each person," he said.
Describing Simeone's vision of football, he added: "It's basically to suffer on the pitch. It is to be suffering, have an opportunity and score it. That's his way of competing. It's not bad but it's different to other coaches."
Follow Felix's return to the Chelsea fold this weekend with Flashscore.
