Alan Cohen said this quote

Gratitude, like faith, is a muscle. The more you use it, the stronger it grows, and the more power you have to use it on your behalf. If you do not practice gratefulness, its benefaction will go unnoticed, and your capacity to draw on its gifts will be diminished. To be grateful is to find blessings in everything. This is the most powerful attitude to adopt, for there are blessings in everything.