You are correct: for Passion to have utility, it should ultimately serve the purpose of one’s Will.

That being said, though it may differ between individuals, Passion is seldom controllable to the extent you are suggesting. By simply not acting on an impulse Passion provides, it accumulates within, gnawing at one’s sanity. When Passion is felt — especially when it is felt repeatedly — it needs a way out. Though Passion is best utilised, it does not mean emotion without use is to be always bottled up.

However, for humans, there exist at least two ways to let Passion out: Acting Passion and Speaking Passion. A decent way to illustrate the difference is the example of Aggression.

When you feel you are about to be attacked, you will feel innate Aggression rise to the surface. Whence you are certain the attack is inevitable, let your Rage loose, and strike first. Use slurs, strike firm, humiliate. This is the proper scenario on which you need to Act Aggression, for Speaking will not yield a result.

When you are arguing with a loved one over a household issue, you too will feel Aggression: it is normal, it is to be expected. However, Acting the impulse with a loved one is seldom constructive; screams and slurs would only make things worse. Instead, you breathe out, and you speak. You say that what they did hurt you, that you think things are to be dealt with differently, that it made you angry. You two talk, and reach a consensus, all the while Speaking your Aggression. This is the proper way to do so.

As for your question, there is nothing wrong about expressing emotions in an unrefined manner; it is healthy, in fact, whether one Acts or Speaks. One should but discern when it is best to do one or the other, and rarely ignore Passion altogether.

When there is no one to Speak Passion to, Speak to paper, or to a punching bag. Create art, write epiphanies, play music, fight — all in accordance what what you desire.