Happiness doesn’t last forever

Hi all

Brooke says life is 50/50 and you need to experience good and negative emotions equally. But when I am experiencing happiness or feeling excited about something happening in my life… there is this thought which pops – this doesn’t last forever and you have to be experiencing discomfort soon. I am failing to experience the happy emotion and preparing myself to experience the other half. Is there something wrong in the way I’m thinking about this ?