Stable emotions don't mean suppressing emotions, because you're human, and humans have emotions. So, emotional stability means expressing your emotions in a stable way, rather than expressing them in an emotional way. Express your anger, but not angrily. Express your sadness, but not sadly. And if you don't express yourself, how can you expect others to understand you? How can they understand that behind your silence, indifference, and poker face, your heart is currently breaking? So, many times, you need to turn the expression of emotions into a healthy and constructive communication between two people, rather than a volcanic outburst of venting. This will help your relationship and allow you to timely express every emotion, emptying yourself in a healthy and stable manner. Let your partner understand your inner world and give them the chance to become your confidant.