My wife asked me this morning, “What do you feel is your core purpose in life?”
The first thing that comes to mind is what Buddha said on his death bed upon hearing his disciples’ pleas for advice: “All created things must pass... strive on diligently”. For me, it doesn’t get simpler or more honest than that.
Put another way:
vayadhammā saṅkhārā appamādena sampādetha
All compounded things, all experiences (mental and physical), all phenomena by their very nature decay and die, and are disappointing. It is through being not-blind-drunk on, obsessed by, or infatuated with, the objects of the senses that you succeed in awakening, or obtain liberation.
And more succinctly:
All things are disappointing, [it is] through vigilance [that] you succeed.
And even more succinctly:
The core purpose of all living creatures
Isn’t the core purpose of any living thing to be alive, alert, and watchful in its environment? The sense perceptions of living thing, however limited, evolved to allow the creature to ‘know’ its environment. If a creature is lax in using its perceptive powers its survival is put at risk. For instance, the one-cell paramecium would use its cilia less, thus fail to sense and capture the bacteria it needs to survive. On the other end of the scale, a person lost in thought, or his cell phone, will fail to see the bus and so risks being run over. Vigilance is evolution’s filter, where over time only the most vigilant pass on their genes.
For other aspects of how Buddha’s outlook applies to all life, see Buddha's Truth Pertains to All Life.