bottle (one's) feelings up

To keep one's emotions totally private, without expressing or releasing them in any way. Usually used in reference to emotions that are particularly painful to feel or difficult to express, such as anger or grief. He needs to find an outlet for all that anger. If he keeps bottling his feelings up like that, he's going to explode some day. Please talk to me—don't just bottle your feelings up. After my dad died, I knew I couldn't bottle my feelings up forever. That's why I started going to therapy.