Assiduity

as·si·du·i·ty  (s-d-t, -dy-)
n. pl. as·si·du·i·ties
1. Persistent application or diligence; unflagging effort.

2. Constant personal attention and often obsequious solicitude. Often used in the plural.

    *  He is a young man of considerable perseverance, he has worked his way for years, under many disadvantages, with great assiduity.
It was said in his obituary that he owed his advancement to unwearied assiduity, good talents, and respectability of character.