In my article titled - "Everything is a Play of Consciousness", I have made the point that the state of our consciousness at the moment of our awakening from sleep, determines the quality of life for the rest of the day. If we feel blissful at the moment of awakening, then it is perpetuated for the rest of the day. If bliss is lacking then the whole day feels indifferent or even miserable.
This phenomenon is due to an in-built mechanism where the mind keeps coming back to the "perceived reality' for that day, which is the state of our consciousness at the time of awakening. This forms the "core consciousness' or the "self' of that individual for that day, with all activities of the mind having this core as the basis.
The mind judges events of the day with this core as the reference point. If the core is blissful then the mind also sees the world as basically blissful. When confronted by problems the feedback from the core anchors the mind to the "blissful reality' and the mind overcomes problems by creating solutions.
This biofeedback from the "core consciousness' maintains the quality of our consciousness, whether blissful or not. The mechanism of our built-in biofeedback explains why positive thinking works. See good, be good and do good may appear to be a moral advice to lead a happy blissful life, but it has a biological basis.