There is a Vietnamese Zen Buddhist Master, by the name of Thich Nhat Hanh, who has promoted the Zen practice of Mindfulness. As I understand it, it is being present to the moment, what you are doing at that moment, present to the sensations, the feelings, the actions you are doing; not let yourself being distracted by other thoughts.
Yesterday, I was in one of the chapels of St. Anthony Shrine, Boston, MA. I was seated in front of the tabernacle, as I have done on many other mornings, saying my morning prayers, as I do on many mornings. I suddenly stopped as I became fully aware that at that moment, I was present before the Son of God, the Bread of Life. And for that brief instance, I experienced something that I find hard to describe.
There is a danger that our spiritual disciplines, our practices, can be so routine, that we can lose our focus on what is happening at that moment. It can be a struggle, but we need to be mindful of the present moment, when we enter into prayer; be aware that we are entering into God's Presence. We open ourselves then to truly experience His Love,
"...so, as we see bread and wine with our bodily eyes, we too are to see and firmly believe them to be His most holy Body and Blood living and true. And in this way the Lord is always with His faithful, as He Himself says: Behold I am with you even to the end of the world (cf. Mt 28:30)." (Admonition I, St. Francis of Assisi)