I'm really enjoying the book The Noticer, by Andy Andrews. This is a quote from one of the main characters named Jones.
"When you focus on the things you need," he went on to explain, "you'll find those needs increasing. If you concentrate your thoughts on what you don't have, you will soon be concentrating on other things that you had forgotten you don't have--and feel worse! If you set your mind on loss, you are more likely to lose...But a grateful perspective brings happiness and abundance into a person's life."