Remaining quiet is hard for a proud person, I know this from my own spiritual struggles. Pride convinces us that we have something of importance to say; something that people desire or perhaps even need to hear. It is a rare thing however that the proud person's perception and reality match. It is more likely that the proud person needs others to hear about his self perceived righteousness.
The passion of pride attacks the mind in particular. Pride is the result of blindness to the reality of who God is and who we are. According to our fathers among the Saints, pride is a disordered passion. "A disordered passion is an excessive feeling or appetite that goes beyond what is reasonable. Passions are a disturbance of the soul contrary to nature, and disobedient to reason" - Clement of Alexandria. In other words, passions are the direct result of an unbridled appetite and delusional fantasies.
Few have been more successful in dealing with the passions as the dessert fathers. Fortunately, they have left us with many successful cures for pride and its delusions. One of the cures is 'quietude'. Evagrious the Monk said: "cut out the desire for many things out your heart. By doing so you prevent your mind from being scattered and thus your quietude from being lost." According to the consensus of these fathers it is a lack of knowing God, and a desire for many things to fill that void that prompts us towards delusion. Consequently, these delusions result in our expulsion of a great deal of hot air to our own demise.
This quietude can be quite a challenge to someone brought up with a Western mindset. In the West we have come to embrace the concept that most things can be cured by education and thus by much talking. In this way of thinking it is the verbal transference of information that saves us. In fact, most folks in the West attend church to be educated, or to use the proper word, to be edified.
By contrast the earlier Eastern and premodern approach accepts the fact that it is by silence that we are most edified. It is by a quiet but constant lookout for our pride, and by quietly turning ourselves around-metanoia that we are saved. I have learned this much, when I want to speak, it's probably best to SHUT UP! And if I must speak, first consider God and my delusions of pride, as well as what I really want to obtain by speaking. Only then consider speaking, or then again perhaps not.