Mental health:

Distractions:

Hydration:

Pilot relief:
A pilot distracted by the urgent desire to urinate is an accident waiting to happen. Such a need is natural on long flights and yet it is rarely discussed openly. An excellent article addressing this problem "To ... Or Not To ...? No Question About It" by Karl and Iris Striedieck in Soaring March 1996, p 41/42. Useful discussions have appeared in contributions to rec.aviation.soaring. For example the January 1996 and March 1998 discussions addressed this issue and probably led to the above Soaring article. Chip Bearden's contribution, republished in 2004 was informative while an amusing 2006 discussion on painless catheter removal led to the May 2006 contribution entitled "The Catheter Saga- A Synopsis" contains useful hints. An excellent reference is Glider Pilot Relief Systems.