In chapter 9 of the famous book of Jewish self-improvement, Orchos Tzadikim (15th century), we find the following formula for happiness: "If a person obtains all that he desires and nothing causing him sadness befalls him, he will constantly be happy. His face will shine, he will be physically healthy, and he will age slowly."
How can we reach this utopian state? First, refrain from desiring what is beyond your reach. The simpler your desires, the greater the chance you will be able to meet their requirements. Anything extra you obtain beyond these demands will give you increased happiness, so you have nothing to lose and much to gain by lowering your demands and expectations. This does not rule out striving for realistic goals, only that you give up your DEMANDS for things that you may not be able to obtain.
Secondly, do not allow common day-to-day occurrences to cause you sadness. (e.g. traffic, burnt toast, etc.) Master a perspective of life that will enable you to at least accept minor hardships without becoming sad.
(see Gateway to Happiness, p.28)