Salam Alaykom. Is it permissable to always be thinking about death and the like such as the grave, hereafter, questioning in grave, etc?? Is it okay to cry when thinking about it? Any rewards that will accumulate for the person that has these thoughts like me? Jazak'allah khair.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Remembering death and not being heedless of it is something religiously required and a person will be rewarded for doing so, as the Prophet said: "You should mention the destructor of pleasures much (i.e. death)." Therefore, the jurists stated that it is desirable for every single person to mention death much. Mentioning death makes a person become ascetic in this worldly life and urges him to perform good deeds and shun off acts of disobedience, even if this leads to crying, because this kind of crying is praiseworthy as it is due to fear.

However, mentioning death much should not stop a person from seeking provisions.    

Allaah Knows best.