It is not often that you get the chance to truly speak your mind. Be it at a meeting at the workplace, be it at a sales pitch to a customer or be it at home with your significant other.
There is always that lingering feeling of 'what might be the consequences?' if you were to speak your mind. It could be a worry of falling into the bad books of your boss because you disagreed with her idea, it could be a worry of letting potential revenues slip by upsetting a customer, it could be a worry of initiating an argument with your significant other.
When fear dictates your actions (or words), you withhold your true feelings and opinions, and feel less alive and whole like Dilbert in the cartoon. This starts taking the relationship with your boss, customer, spouse towards a transactional one and saps enthusiasm.
You can only re-invigorate the relationship if you can discard your fear of consequences. If it is not conducive to do so, then you had better start looking for a new one.