The reality is, this planet is only so welcoming to life
Does this refer to the planet ruling the 6th, or to the one that is placed in the 6th?
It sounds like the 6th represents the forces of nature, such as friction, gravity, and weight, against which we can use our will to build up some strength, resistance, resiliance, or strategy against. But all organisms succumb to friction and gravity in the end. So that which makes us stronger, indeed does eventually kill us?
I always thought the 8th, and even to some degree the 12th, represented death more than the 6th would though.
More scorpio stuff, this one is not under mental illness section but I have seen it in charts of alcoholics especially with planets in trishita/thirsty avashta.
MERCURY IN SCORPIO: This combination makes the native a gambler, debtor, drunkard, atheist, thief and an impoverished person.