For everyone that has been saying Jiren is a non-character or boring obviously haven't been studying his interactions with other members of his universe and universe 7. His quotes pack so much meaning that people overlook. Jiren puts all his faith in his own strength, and looks down on those weaker than him. Even so, he claims that he seeks "that which lies beyond strength." What could he be referring to? I think he's still looking for the answer to that, but he may finally get it when he witnesses Goku's mastery of Ultra Instinct. With all the focus that's been placed on Jiren's meditation, it's safe to say that he feels confident in his strength and instead chooses to focus on his mind. The energy from his glare, that barrage of punches as he closes his eyes; these attacks seem to stem from pure focus. Ultra Instinct, on the other hand, is about taking the mind out of the equation and letting every part of your body react on its own, a feat that the Gods themselves struggle to achieve. I don't believe Jiren was aware of UI and what it means when he first fought Goku, and even later when he observed his fight against Kefla. To someone who's put so much emphasis on sharpening his mind, the idea of removing it from the equation entirely must seem preposterous. It's in their final battle, when Goku finally masters this ability, that Jiren will truly understand what he's up against. He'll also have to reconcile with the reason why Goku, a mortal far weaker than himself, could obtain such a power when he could not...
"Trust begets nothing."
This sentiment seemed to strike a nerve with Goku, and I believe it's Jiren's greatest weakness. Whereas one warrior, scarred from childhood, foregoes emotion and true relationships and relies solely on his own strength, the other feeds on the trust his friends and family bestow upon him, which ultimately aids him in trusting himself, and his own instincts.