A lot of people believe that some emotions are ‘good’ and others are ‘bad’, but that isn’t the case. We have feelings for a reason and they simply are what they are.
Finding a creative outlet to explore and release any emotion can be greatly beneficial. If creative writing or music isn't your thing, just vocalising it with someone you trust can work in the same way.
Allow yourself to feel sad. Instead of shoving down or ignoring this feeling try to be curious towards it: why did this sadness arise? Can you do anything to make it better? Are you able to observe, accept, and feel it?