"Be True to Me, Non-self and the Why." - anonymous
Brainstorming the purpose behind everyday motivation in life, it seems to me there are three primary drives. The drive for self, the drive for others, and the drive for the thing itself. These modes of purpose operate in overlap with each other creating a more robust motivational behavior.
Whether we like to admit it or not, we do many things primarily for selfish reasons. Much of this is evolutionary, supporting our daily survival, our mental well being, and even our genetic transcendence. The obvious selfish acts fulfill the senses we've evolve to ensure good nutrition, bonding with family, seeking mates and entertainment. Even much altruism can be traced back to defending the self by reinforcing the tribe for survival the self.
Yet, altruism can reach beyond any realized or perceived self preservation. As humans we can be transformed by our ideals. Thus once we become a protector of the environment, there may be some benefit for the self or tribe, but we can transcend to caring for the thing for the sake of its own survival. This, of course, can manifest in the love for other individuals too (human and non-human). When we put the well being of another truly ahead of ourselves, our motivational purpose centers on the external.
Abstract ideas themselves can be motivation as well. Ideals, feelings, knowledge, adventure, etc. can be motivational beyond self and others. Indeed, pursuing these abstractions often can provide benefit to self and others, but they can manifest as entities in and of themselves. The pursuit of ethics, information, or experiences for the betterment of the abstraction is itself in this case motivational.
Together these three modes combine to influence our purposefulness in life. Motivations can, however, mislead us too if we don't keep goodness in mind. A good rule of thumb is to justify both the means AND ends of ones pursuits. In this way, a feedback loop of assessment of ones actions can be made toward achieving ever better purposes.