Mourinho spoke of Chelsea being more expressive and taking the initiative earlier in the season but concerns about dropping out of the UEFA Champions League qualification spots prompted his U-turn to a more defensive set-up.
He has not pinpointed the specific time of the change, but it appeared to come in the goalless draw at Arsenal two days before Christmas after defeats to Newcastle, Stoke and Sunderland in the Capital One Cup in November and December.
The Portuguese's sterner style was highlighted in the 2-0 victory at Liverpool last weekend, a result which has left them now needing just one point to ensure automatic qualification for next season's Champions League.
Chelsea, who host struggling Norwich on Sunday, also still have a slim title chance - although they are relying on Manchester City and Liverpool slipping up - and Mourinho has no regrets about his mid-season readjustment.
"I knew what I was doing," he said. "We are still in a position, mathematically, to win the Premier League and in the Champions League we reached the semi-final and we had one foot in the final.
"There are moments when you have to go for the strategical point of view if you want to have a chance to compete for what we compete.
"At a certain moment, if you don't go for a bit more stability and a bit less development of a certain philosophy, it's a big risk.
"I made the decision to stop that evolution in the style and philosophy of play and I went in the direction where I felt it was the only way, that, with this team and with these players, we could get results.
"It's not a cup. I don't want to get a bonus for finishing top four, no way, no way; the moment I think like that I'm in trouble.
"(But) there was a moment that I felt this Premier League was so dangerous that was the big risk for every one of the big teams to be out of the top four.
"Don't forget we had lots of matches, and long periods this season where we produced fantastic football, even away from home, but we weren't the killer profile.
"Even our wingers and our number 10s - Eden (Hazard), Oscar, (Andre) Schurrle and Willian, amazing season by Willian - need to score more goals, they need to be more clinical.
"They need to play and produce according to the way we play. We had lots of matches where we created lots.
"At Everton in September we should have been 5-0 up at half-time, but we were 1-0 down. Things are not sometimes like people like to say.
"We build certain bases that we need to recover in the beginning of next season, especially when we have this little, little transformation and improvement in our squad that we need.
"Next season we will start the season, hopefully, I can have finally the feeling of 'okay, we are going to try (to win the title) and we really feel we can'.
"But even so the next summer I think we're going to feel the danger of missing out on the top four.
"The difference between being champions and outside the top four is a small difference."
Watch Chelsea take on Norwich live on Sky Sports 1 at 4pm on Sunday.