Self-devotion, n.
The act of devoting one's self, or the state of being self- devoted; willingness to sacrifice one's own advantage or happiness for the sake of others; self-sacrifice.
Shades of meaning
Fernald has no entry of its own for self-devotion; he lists it under self-abnegation.
Where he writes about it:
Self-devotion is heart-consecration of self to a person or cause with readiness for any needed sacrifice. — from self-abnegation