Let us start our search for happiness from the very beginning. That is from the beginning of the universe. The most plausible and widely accepted theory of the creation of the universe is the 'Big Bang' theory of creation. According to it, the universe is created from an explosion in the super condensed material and consequent expansion of material. However, even if all the conditions for the creation of the universe were right at the beginning, many factors had to be right for the consequent formation of the universe. For example:
Our universe is expanding like a polka dotted balloon which is being blown out. Each dot (representing a star or a galaxy) on it is distancing itself from each other. Now, if the rate of expansion of the newly created universe had differed even very minutely from what it were actually, there would have been no universe. A little slower and the cosmos would have collapsed back, a little faster and the cosmic material would have long ago completely dispersed.
If the density of the universe were a little more, the universe would not be expanding but, due to the force of attraction of atomic particles, contracting, ultimately collapsing. If the initial density were a little bit less, then the universe would be expanding far rapidly than now and no stars and no galaxies would ever have formed.
Both the mass and the volume of a proton are incomparably larger than those of an electron; but strangely enough, these two particles have equal (though opposite) electrical charges. Because of this fact atoms are electrically neutral. If the atom was not neutral electrically, each atom would repel the other and the entire universe would explode.
The four fundamental forces in the nature, in decreasing order of intensity, are Strong nuclear force, Weak nuclear force, Electromagnetic force, and Gravitational force. The difference between the strongest and the weakest is about 25 followed by 38 zeroes. Still within that great range the individual and the comparative magnitudes of the forces are delicately balanced otherwise the universe would not have existed.
If the creation of the sustained universe was a miracle, the evolution of life on it was also the same... Had our sun been 30% larger it would have been burnt out in four billion years, too short a time for intelligent life to evolve. Had it been smaller 95% of stars are smaller than the sun other difficulties would have followed. Similarly, had the sun not been a source of steady energy for billions of years, had the orbit of earth around sun been a bit narrower or wider, had planet Jupiter been too close or too far to save earth from the rain of steroids, had moon not been so improbably large to stabilize the tilt of the Earth's axis to around 23 degrees, had the solar system's position in the galaxy been too near the edge or too close to the middle, advanced form of life would have been impossible.
Carbon based molecules can only survive between the limits of 120 and -20 C and earth is the only planet whose average temperatures fall within those limits. When one considers the universe as a whole, coming across a range of temperatures as narrow as this is quite a difficult task because temperatures in the universe vary from the millions of degrees of the hottest stars to absolute zero (-273 C).
Nearly all of the radiation emitted by the sun falls into a single band that is 10-25 of the whole spectrum. Radiations which are necessary and conducive for life fall in this narrow band. This is also the only radiation under which photosynthesis works and our eye is able to see.
Water also has extraordinary properties conducive for life below 4 C it expands (so that even if ponds etc. are frozen at surface underneath water is not), highest latent heat, high thermal capacity, high thermal conductivity while that of ice and snow is low, high surface tension, and viscosity, etc.
The first step to happiness is to realize this happy but impossible oddity of creation and life. We are extremely lucky to have a universe, and even more so to have a universe full of life. Since life is so improbable, Earth may be the only planet on which there is life. To be born as a human being is the happiest thing which could ever happen to anybody!