no it's not.
If you're a student capable of 99 and you get 89, you'll be incredibly disappointed, and rightfully so. You haven't achieved anywhere near your potential. Why should you be proud of that? It's not about thinking positively or negatively, it's about your expectations, whether they are valid or absurd.
Everybody is capable of getting 99. Its just that some people dont want it or dont need it. Personally i wanted to be a doctor in about year 9, but in year 10 i thought, im not gonna take what everyone else thins is good. I decided that i didnt need a UAI of 99, i didnt even need one of 90+. All i need in 85, and ill be happy to get into my course.
Many people have forgotten about the SC. Its gonna be the same here. At Uni the only time people will ask your UAI is when you first start, then you can forget about it for the rest of your life.
I didnt start paying the absolute shit of my marks when i received them. Although im gonna get a UAI really close to the cutoff. The reason, YOU CANT CHANGE THEM! (conditions apply). My aims were much higher than my expectations, it gives leeway for unwanted results.
I find it annoying that some people say they are smarter than people with a lower UAI. There are many factors.