People often do not give thanks for the blessings they receive. Those blessings can come through other people, directly from God, or is ways that surprise us- -one might say, by the back door. 

The Grace of God is all around us. It is active in our lives. The people whose lives intersect with ours shine on us and we, in return, shine on them. God is also present in creation. Whether that Presence is in other people or in creation, it is right that we express gratitude.

If we speak it aloud, it is a way of answering God, a prayer that tells God we see the Presence. Such a spoken thanks may empower the one thanked to continue, deepen or enlarge their ministry. Giving thanks is a spiritual practice, just like learning forgiveness or prayer or patience.

You can read more from Martin here: http://esrquaker.blogspot.com/2013/09/gratitude.html