Responding to “How’s it going?” is a common social interaction that can be used to show empathy, build rapport, and maintain relationships. There are many different ways to respond to this question, depending on the context and your relationship with the person asking.
In general, it is considered polite to respond with a positive or neutral answer, even if things are not going well. This shows that you are appreciative of the other person’s concern and that you are trying to maintain a positive attitude.