In Spanish we say ... cría fama y acuéstate a dormir ( In English would be something like ... Rest on your laurels and go to sleep)
It is difficult to recover from a bad opinion, but for those of us who work with people, I think the best attitude is the one you describe. Not all of us are the same with everyone, but with cookies the success is guaranteed 🍪😃
The thing is, I didn't go to my initial meeting with this guy with the preconception he had a bad reputation, I went there with a clean slate as I'd put aside the comments and things I heard. That allowed me to form my own opinions then move on from there.
Of course, reputation can often precede a person and a bad one can be difficult to recover from as you say.