(n.) work or performance far beyond that which is required
In the Catholic Church, supererogation is work or penance that exceeds that which is actually divinely commanded. Such good deeds—properly known as ‘works of supererogation’—are considered to be held in store by the church, so that they can be allocated via prayer, when required, to offset the deficiencies or delinquencies of sinners. Fittingly, the word supererogation itself derives from a Latin root literally meaning ‘to pay out’.
In this strict theological sense, supererogation established itself in the language in the mid sixteenth century. But over time, the word has come to be used more loosely to refer to any work, duty, or performance considered above and beyond that which is actually required or expected.
So if you are the kind of person who habitually overperforms at work—especially in order to make up for the deficiencies of others—then supererogation is the word for you.