Bale is expected to make just his third Premier League start since returning to Tottenham on loan in Sunday's visit of Burnley, having impressed in both legs of the Europa League last-32 and in last weekend's defeat to West Ham.
Bale struggled to make an impact until this month and Mourinho has occasionally appeared frustrated with the 31-year-old winger, saying he was "doing my best" after leaving him on the bench for the defeat to Chelsea earlier this month.
Bale has since found some form and he scored a brilliant first-time effort in Wednesday's 4-0 win over Wolfsberger, which Mourinho believes is a sign of confidence.
"Mental is always a consequence of the physical," said the Spurs boss when asked if Bale is as fit as he has been since returning to the club. "If a player feels great, if he is playing 100 per cent and if the feelings are all good, there are no psychological problems or fears or barriers.
"When you have little worries and especially when you have a recent history of injuries, it’s normal to have some fears and these fears have a consequence. But lately he has been fine.
"It’s just a question of how many minutes he can play and how many days he needs to recover between matches. He looks happier than ever, he looks confident.
"In training you can see he has his confidence back, the way he hits his shots.
"You could see from his goal on Wednesday. It was a confident shot. A player with fear or negative feelings would never have hit that type of shot. To strike the ball that way, I think that strike means a lot. It means freedom.
"It means freedom in relation to the brain muscle. For this, you need to be in a good condition. He is in the best condition since he arrived."
Bale missed the FA Cup defeat to Everton earlier this month after suffering discomfort in training, with Mourinho insisting he was not injured but sidelined due to "some feelings".
Mourinho insisted the club trusts Bale to make calls on his own fitness and said they had to continue to be cautious with the winger, whose career has been disrupted by injury.
"He is a player with a lot of experience and a player with a lot of experience they know their body better than anyone," Mourinho added.
"There is no coach, no fitness coach, no sports scientist, no medical that knows the better than a very experienced player especially a player who had years of small problems, bigger problems, but situation that had have an had an influence and an impact on the past couple of years of his career. And we trust him. We trust his experience and analysis.
"And everything with him is done with a great participation of everyone.
"Because everyone wants the best for him because in the end the best for him is the best for Tottenham.
"So to have him and giving us important contributions is doing that bit by bit. Of course we want that in a more continuous way. Of course we have very important Premier League matches, a crucial final and crucial every minute of every game in the Europa League, so the more that we have Gareth, a player with his quality and confidence and experience and know how of big moments, the better.
"So we have to be careful and trust a player with a lot of experience."