There is a wonderful exercise called Naikan, developed in Japan, geared to addressing this issue [gratefulness]. It works to break our focus upon all that we lack, and put our attention instead on what we are receiving. This exercise is truly Zen in motion, in everyday life.
Spend about thirty to forty minutes a day with this exercise. (There are also Naikan retreats available, where it can be done all day long.)
Make a careful, specific list of all you have received today. Be careful not to overlook small things. Everything matters.
Make another list of all you have given. (Usually we think we are giving all day long and receiving very little. This list will surprise you. Don't leave anything out.)
Now make a third list of any trouble or pain you may have caused anybody. Some think this list will induce guilt. It may or it may not. The purpose of the list is simply to reverse our usual thinking, where we feel hurt and disappointed by others most of the time, and do not look at what trouble or pain we may have caused.
— Brenda Shoshanna in Zen Miracles