The mind is the source of happiness and unhappiness by what it chooses to compare the experience with. If it chooses to compare it to something worse then it will create happiness, gratitude and pride but if it chooses to compare it to something better then it will create unhappiness, bitterness and envy.
Gautama BuddhaMen give up one thing to take up another, but in spite of numerous changes they do not find peace. They are no better than monkeys who let go one bough to take hold of another, only to let it go again.
Gautama Buddha