"Frustration arises from the gap between expectations and attainments. When your expectations are fulfilled by your attainments, and when your desires are reachable at your income, you feel satisfied rather than frustrated," says Dave Myers in The Pursuit of Happiness.
He describes an experiment about how your thinking affects your life satisfaction:
"State University of New York at Buffalo psychologists Jennifer Crocker and Lisa Gallo tested the wisdom of that old song, "Count your blessings, name them one by one." After five times completing the sentence "I'm glad I'm not a . . ." people felt relatively happy and satisfied with their lives," writes Myers.
"By contrast, those who counted their unfulfilled desires, by completing sentences beginning with "I wish I were a . . ." came away feeling worse."
Keep reminding yourself how lucky you are, and you're more likely to be happy. If you compare yourself to others and focus on what you wish you were or wish you had, you'll be less satisfied with your life.