When you knowingly or unknowingly break someone's trust, cheat, or use them for your selfishness, you start feeling self-guilt.
When you set an objective and fail to fulfil it, you start feeling ashamed of yourself; this is self-guilt.
If you have abused someone physically or mentally and you feel that you have done it wrong, then it definitely comes under the category of guilt.
If you are not able to achieve your objectives because of your principles, then you are not going to get anything except regret.
You are prioritizing your personal needs, even when you internally believe that you should take care of the needs of others.
If you have a comparative view of yourself, you will suffer from an inferiority complex. That's enough to make you feel guilty.
Knowingly or unknowingly, a person commits some mistakes in their life that they regret in the future; they've nothing but shame, emptiness and an inferiority complex.