"I am a good person."

Everyone in this world will not think twice to say "I am a good person."

No matter whether a person is really good or bad, he/she will hold himself/herself in positive light.

Rarely to never will a person honestly say he/she is bad, or not good enough.

So here are 2 criteria that I use to judge whether a person (myself included) is good or bad:

1. How a person treats another that is weaker than he/she is.
2. How a person treats another that is different than he/she is.

In combination, a person can be determined to be either good or bad based on how he/she treats another that is weaker and different than he/she is.

Weaker as in inferior, more stupid, poorer, less skilled, etc.
Different as in different race, different social class, different religion, etc.

If a person violates any of the 2 criteria above, then he/she is not a good person.
By fairness, he/she should instead say "I am a neutral person, susceptible to both good and bad conducts in accordance to selfish interest."

Nobody can maintain the standards consistently.
So by right, do not say "I am a good person" so casually.
Otherwise, even a criminal can say the same about himself/herself; "I am a good person."