This is really common, its talked about over and over in psych media. Idealization comes to a halt when let down. Or idealization/devaluation.

I had a strong idealizing transference (in love, not seeing as perfect though) for a long time, it comes from a young place. I still have it despite being angry at him for being so withholding. Mine doesnt ebb flow that much, i feel ive always had fairly realistic expectations of him.

But if you sort of see your T as perfect, which is anothet type of idealizing transference, a mistake will change your mindset of course.