Mourinho says after two years of battles for Bale at parent club Real Madrid, it was always going to take time for the Welshman to find his best again.
Mourinho said: “Gareth is a player that I always loved. In fact he went to Real Madrid because I spoke with the president when I was there and told him he was a guy I like very much.
“As a person he's a really, really nice guy, a dressing room guy. The reasons he didn't reach in this period the level that Tottenham supporters remember him is a complex answer.
“If Gareth was here we could speak a little bit about it but just by myself I'm not comfortable. If he's happy when he sits on the bench I don't think so. I honestly don't think so.
“Everybody knew that in the past couple of seasons, in Madrid, they were not easy for him. So let's go, step by step, and try to get the best out of him."
Bale, 31, does seem likely to return to Madrid in the summer when his Spurs loan expires but Mourinho insists that has not been formally discussed yet.
Mourinho added: “There was not even a second of discussion about that. Gareth is a player on loan until the end of the season. Not one second of discussion.
"We are speaking about, of course, Gareth, himself, Real Madrid, Tottenham, but I promise you, not one second of discussion."