The anguish of hearts is a gift that reflects the compassion which Allah has placed within you. The tenderness of the heart and the tears that roll from your eyes are also a manifestation of Allah's compassion [which He has endowed you with]. Consider the twinge of your hearts and your moistened eyes as Allah's bounty. The hearts that remain unmoved by the suffering around us and the eyes that fail to well with tears are a sign of one's being removed from Allah's favour, of being impoverished. Remember well that this tenderness of emotions will act not just as the healing balm but will also be your support and a means of reward in the Hereafter.
Do bear in mind that even in sorrow you must have the intent to emulate the Prophet, blessings and peace be on him. This will bestow proximity with the Prophet and provide you support. What's more, you will also be rewarded for enduring this grief and affliction, and you will also be blessed with Allah's love for having followed in the footsteps of the Prophet.
Your hearts and eyes are not in your power. Nor is it required to exercise total control over your hearts and eyes. Rather, the compassion which your eyes and hearts give vent to is a gift from Allah Himself. But keeping the tongue in check is important and lies within your power. Do not say anything which is against the spirit of rida-bil-qada (total acceptance of what Allah has decreed). Do not resort to lamentation and bemoaning, nor give vent to complaint and grievance, nor be seized with feelings of hopelessness and despair.
"Dying and Living for Allah" - Khurram Murad