Life is sometimes unfair.
A reaction to the unfairness is to be unhappy. We feel that if we are happy then we are accepting the unfairness. We feel that if we are unhappy then we are validating the unfairness.
Either way, it is an unproductive strategy.
A better strategy is to call out the unfairness and be happy anyways. Whether you are happy or unhappy doesn’t change the unfairness.
This is a strategy that equally applies to the unfairness that is the result of another person. Just because you are happy does not make the unfairness right. Separate the two and make sure that the feelings around the unfairness do not get intermingled with your happiness.
You have the right to be happy regardless of what happens in life.