Mental prayer in my opinion is nothing else than an intimate sharing between friends; it means taking time frequently to be alone with Him who we know loves us. The important thing is not to think much but to love much and so do that which best stirs you to love. Love is not great delight but desire to please God in everything.
The Collected Works of St. Teresa of Avila: Volume 1 (ed. ICS Publications, 1976) - ISBN: 9780960087624