Does God's lack of mercy toward His servants – due to the presence of the sick, the disabled, and wars – justify contemplating suicide?

Allah is merciful to His servants. The afflictions that befall Muslims are for a profound wisdom. Allah tests the believers to see who among them is best in deeds, and so that various forms of servitude, such as patience, supplication, and contentment with divine decree, may become manifest from them, and so that their ranks may be elevated.

This faith repels whispers (waswas) that neither harm nor affect the soundness of faith, as long as you detest them and are repulsed by them. So continue to strive against them and repel them by contemplating Allah’s wisdom. You will be rewarded for that. Beware of suicide, for it is one of the gravest destructive sins.