Thanks to Rabbi Neal Loevinger for introducing me to this term, sitzfleisch - here is an amazing quote about it, courtesy of Wiktionary:

Sitzfleisch (uncountable)

The ability to endure or carry on with an activity.

1947, Frank Vigor Morley, "My One Contribution to Chess", Chess Notes, Faber & Faber (1947):
Sitzfleisch: a term used in chess to indicate winning by use of the glutei muscles--the habit of remaining stolid in one's seat hour by hour, making moves that are sound but uninspired, until one's opponent blunders through boredom.