Doubtless there is need for me to do my best to explain these spiritual subjects to you, for we often hear how beneficial prayer is for our souls; our Constitutions oblige us to pray so many hours a day, yet tell us nothing of what part we ourselves can take in it and very little of the work God does in the soul by its means. It will be helpful, in setting it before you in various ways, to consider this heavenly edifice within us, so little understood by men, near as they often come to it.
- St. Teresa of Ávila, The Interior Castle

 Prayer is a beatiful way of communicating with Jesus Christ, it also has numerous benefits, affecting our daily lives in many ways.

With time and practice, we learn to know ourselves better, and as such, we make ourselves more available to others, and to Him.

This gained self-awareness makes us more attentive in our daily activities, during prayer, in our times of silence, in our actions. When it comes to praying during Mass, we are more "present": we get to  truly experience moments like the entrance hymn, the preparation of the gifts ("Pray, Brothers and Sisters, that my sacrifice and yours may be acceptable to God, the Almighty Father"), the prayer after communion, etc. 

When entering our castle, we encounter God, but we also encounter ourselves. We learn about ourselves, and about God's plan for us. 

Remember, we must get to heaven, and it would be madness to think we could do so without sometimes retiring into our souls so as to know ourselves, or thinking of our failings and of what we owe to God, or frequently imploring His mercy. Our Lord also says, ‘No man cometh to the Father but by Me' and, ‘He that seeth Me seeth the Father also' ".
- St. Teresa of Ávila, The Interior Castle

We are changing our outlook, by trying to see things with through the eyes of God instead of our own.

As St. Teresa assures us, mental prayer reinforces our extraordinary friendship with Christ: 

If you become accustomed to having Him at your side, and if He sees that you love Him to be there and are always trying to please Him, you will never be able, as we put it, to send Him away, nor will He ever fail you. He will help you in all your trials and you will have Him everywhere. Do you think it is a small thing to have such a Friend as that beside you?
- St. Teresa of Ávila, The Way of Perfection

More people than we think believe that they are capable of practicing silent prayer, when no one taught them how to do it. Without this meditation, baptised people grow weary, their actions become meaningless, even their faith starts to wear out.
                                                                                                  John Paul II (24/09/1982)

Let Us Pray with St. Teresa of Ávila

Find a time during the day to enter into a state of mental prayer.