Is it permissible to weep during prayer and prostration? Should one avoid sadness during prayer? How can one control emotions to achieve this? Is it permissible to supplicate in prostration in a language other than Arabic?

If a Muslim is afflicted by hardship, the best thing to turn to is prayer. The Prophet, peace and blessings be upon him, used to pray whenever he was troubled by a matter. Weeping during prayer, if it is out of fear of Allah, is desirable and permissible; it is a characteristic of the humble. If the weeping is due to a worldly affliction, and one is overcome by it and cannot suppress it, then there is no harm, and the prayer is not invalidated. However, if one is able to suppress it but does not, and gives in to it, and it is audible, then it invalidates the prayer according to the four Imams. Some scholars stipulated that for the prayer to be invalidated, two letters must be audibly produced. The afflicted person should fear Allah and be patient, and not dwell on their misfortune. They should focus on their prayer once they enter into it, and strive to attain khushu' (devotional humility).

There is no harm for someone who is not proficient in Arabic to supplicate in their prayer in the language they are proficient in.