The problem with using ChatGPT with sentiment analysis is exactly that; it can't be relied upon. But, we can increase our chances of correct output by using chain-of-thought prompting with few-shot examples.
If you don't know CoT prompting and few-shot prompting, please refer to this.
Now, for your case, you can use a prompt like this-
Classify the sentence as positive or negative.
Think step-by-step, and provide reasoning why the text is identified as positive or negative.
For example,
Sentence: 'Same S##t, different day'
Sentiment: The sentence uses s##t. S##t is publically accepted as vulgar or profane. So, the sentiment is Negative.
and
Sentence: 'This product has changed my life, I am so much more productive now'
Sentiment: The product that is being talked about has made the user more productive. Productivity is generally associated with positivity. So, the sentiment is Positive.
Sentence: <<Paste your own sentence here>>
Sentiment:
Here, we are asking ChatGPT to provide reasoning for its decision and also use our examples to remember how step-by-step reasoning works.
Now, while this should work well, it still will give bad results once in a while as ChatGPT is finetuned on human textual data and separately forced to accept some things as positive or negative.
Consequentially, a sentence that you consider as positive/negative might not be looked upon in the same way by ChatGPT.
UPDATE: According the comment, it is absolutely correct that even seemingly vulgar words can be used in a positive context, a modified prompt in that case will look like this-
Classify the sentence as positive or negative.
Think step-by-step, and provide reasoning why the text is identified as positive or negative.
For example,
Sentence: 'Same S##t, different day'
Context: The context seems to be that of frustration where the speaker is frustrated and/or angry at the metaphorical same s##t or mundane tasks.
Sentiment: The feeling is that of frustration and boredom about something. So, the sentiment is Negative.
and
Sentence: 'This product has changed my life, I am so much more productive now'
Context: The context seems to be that of admiration of a product that helped the user in some wah and made their life easier.
Sentiment: Productivity is generally associated with positivity. So, the sentiment is Positive.
Sentence: <<Paste your own sentence here>>
Sentiment: