The Blues beat PSG 2-0 to reach the last four of the Champions League on away goals, and the captain says his manager's preparation gave the hosts the edge at Stamford Bridge.
Laurent Blanc's side won the first leg 3-1, leaving the Stamford Bridge side needing a fine turnaround to progress. Andre Schurrle struck a quarter of an hour after replacing the injured Eden Hazard in the early stages of the game.
With Chelsea needing another goal to go through, Mourinho introduced strikers Demba Ba and Fernando Torres in the second half, and Ba duly delivered with a late strike to send the Blues into the last four on away goals.
"I thought at 1-0 we always give ourselves a chance," Terry told ITV. "We worked a lot during the week on scenarios; 1-0, 2-0, 3-1. Demba comes on, we've hit the big man and he scores a great goal. Every scenario we had a gameplan and once again we got it right.
"This competition means a lot to us. The manager's been very successful. We've experienced it once and the disappointments over the years as well. It keeps you fighting and keeps you believing and that one time winning it, believe me, it's the best feeling ever."
Ba was delighted with his contribution from the bench, telling ITV: "It went so quick [the goal]. I was on the floor then I looked at the goal and I saw the ball was in the net. It was a big joy for everyone. First of all I just do what I have to do when I get chances [to play] and I didn't have chances this season but I just took it."
Mourinho — who has now won 15 of his 22 Champions League games in charge of Chelsea at the Bridge — insisted that he wasn't celebrating after dashing down the touchline following Ba's late strike.
He told ITV Sport: "No, not to celebrate. To tell Fernando [Torres] and Demba [Ba] the changes we had to do. Because there was still three minutes plus extra time and playing the way we were playing was too risky."