sedulous

sedulous \SEJ-uh-luhs\, adjective:

1. Diligent in application or pursuit; steadily industrious.
2. Characterized by or accomplished with care and perseverance.

He did not attain this distinction by accident but by sedulous study from the cradle forward.
-- Alexander Cockburn and Jeffrey St. Clair, Al Gore: A User's Manual

This writing is clearly the product of sedulous art, but it has the flame of spontaneity and the grit of independence both as to mode and spirit.
-- "The Wonder and Wackiness of Man", New York Times, January 17, 1954

And so he reminded the legion that, even though his veneration of his country's flag may not have inhibited sedulous avoidance of the inconveniences of serving under it, he is a patriot so wholehearted that he signed the Arkansas law that forbids flag-burning.
-- Murray Kempton, "Signs of Defeat In the Wind", Newsday, August 30, 1992

Sedulous is from Latin sedulus, "busy, diligent," from se-, "apart, without" + dolus, "guile, trickery."