This thread gives some more detailed recollection of past stamina experiences
http://eqmac.com/forums/viewtopic.php?f=1&t=9774 (they mention things happening when the yellow bar is under 20% and your STA stat is under a certain number, such as a loss of other stats).
A STA greater than (100?) a certain point would remove this stat loss however - I'll keep digging for past info.