Roshi John Daido Loori has said that expressing gratitude is transformative. It is just as transformative as expressing complaint.

Growing in What You Search For

Roshi John Daido Loori asks us to imagine an experiment involving two people: One spends ten minutes each morning expressing gratitude, while the other spends the same amount of time complaining. One subject says, "I hate my job. I can't stand this apartment. Why can't I make enough money? My spouse doesn't get along with me. That dog next door never stops barking and I just can't stand this neighborhood." The other says, "I'm grateful for the opportunity to work; there are so many people these days who can't even find a job. I'm grateful for my health. What a gorgeous day; I really like this fall breeze." They do this experiment for a year. It is guaranteed that at the end of that year the person practicing complaining will have deeply reaffirmed his negative "stuff" rather than having let it go. The one practicing gratitude will be a very grateful person.

More Science of Gratitude

5 Scientific Facts That Prove Gratitude is Good For You
http://my.happify.com/hd/5-scientific-facts-that-prove-gratitude-is-good-for-you/

HOW GRATITUDE AFFECTS THE HUMAN BODY
http://www.huffingtonpost.com/2015/03/30/gratitude-effect-body_n_6510352.html

CLEARING SPACE IN YOUR HOME CAN CLEAR SPACE FOR GRATITUDE
https://www.cohesivehome.com/blog/how-clearing-your-space-creates-gratitude

YES EXPANDS
"Cynicism masquerades as wisdom, but it is the farthest thing from it. Because cynics don’t learn anything. Because cynicism is a self-imposed blindness, a rejection of the world because we are afraid it will hurt us or disappoint us. Cynics always say no. But saying 'yes' begins things. Saying 'yes' is how things grow. Saying 'yes' leads to knowledge. 'Yes' is for young people. So for as long as you have the strength to, say 'yes'." ― Stephen Colbert