As I rely quite thoroughly on God, I suspect I might fall outside your definition of rationalist. But.
You deserve a huge round of applause for pointing out so eloquently just how amazing so-called "ordinary" life is.
Let me add
Resist Parasitism: The power holder is almost completely encased in a self-regenerating barrier which blocks entrance to small parasitic lifeforms. In addition, his or her flesh and blood are filled with invisible essences which are fatal to most external lifeforms which attempt to steal his or her life energy. This allows the holder to survive even in environments completely infested with parasitic attackers.
Regeneration: The user of this power can gradually restore their physical body to full health following most illnesses and injuries short of death. Though material components may be used to hasten the process, regeneration can proceed without them and without any conscious effort whatsoever. The power may be used an unlimited number of times and may apply to multiple injuries at once.
Share Blood: The wielder of this power may speed another's Regeneration (see above) by contributing a portion of his or her life force. The contribution does not significantly affect the giver's health, although he or she is advised to drink extra liquids and avoid heavy lifting for the subsequent four hours. By custom, a wielder of the power is awarded cookies immediately afterward.