At the beginning of the Confession of Sin during Holy Eucharist, there is a rubric stating "Silence may be kept." before we continue with the form of Confession.
This moment of silence may be optional, though it is very important. The time of silence offers us the chance to reflect on what it is we are confessing. It is the opportunity to reflect on our sins.
Having had the time to reflect, we can then say the words of Confession in a truer way. Not only are we more cognizant of our sins as we speak those words, we can also now focus and be mindful of what we are actually saying and offering up to God.
Taking that moment of silence helps us confess better. It also makes the moment of Absolution all the more real and wonderful for us in our lives.