I think I understand that which you are trying to convey.
However humans are creatures of a balanced nature. Meaning they consist of both positive and negative energies. Every one of us is made up of a different variation of these two energies. Truly, no two human beings are exactly alike. So being 100% nice all of the time would be against the original way we were designed.
I will add, being nice certainly is not a bad thing 😉