CBT and DBT can definitely help, learning to identify cognitive distortions will help temper your emotions. But in my experience, that isn't really going to help all that much with bringing up repressed emotion. Maybe some other sort of psychotherapy could help with that, but personally I've been finding a lot of benefit from intense exercise and mindfulness. This helps me from spiraling into negativity because I can't express myself. I was always told things like "just say OK then do it".
As far as expressing yourself... for me, I find I need to be proactive rather than reactive, as in not letting emotion build up so it gets so intense that it makes talking about it uncomfortable for everyone. Sometimes this means saying something, sometimes it means consciously choosing to let something go and sticking behind that decision. And then aside from that, learning that it's ok to have negative thoughts but it's important to temper them when choosing to express or act on them. How you express your negative thoughts at work will probably be very different than how you would around your close friends, so just be mindful of how you are coming off.
For me the balance comes from learning to value myself enough to care about my likes as well as dislikes, but not overvaluing myself to where I'm foring my values onto those around me.