If you're anxious, angry or upset, the emotion will rattle around in your subconscious until it's released. Not expressing how you feel doesn't mean the emotion disappears.
It might manifest as a regrettable action later down the line or an illness. You can guarantee it will come out at the worst possible time.
Talking is powerful. Suppression is dangerous, both for your mental and physical health.
If you don't want to chew your friends' ears off or depend on counselling, maybe you could get some coaching or start a diary.
There is something self-soothing and cathartic about getting your thoughts out of your head and down on paper. It's like self-talk (without the madness!). And like talking, it's great for releasing the suppression.