What is the Islamic advice for a Muslim who suffers from physical deformities that have caused him despair and depression, and fears that his prayer for death may be a sign of his despair in Allah's mercy?

This world is a house of trial, and patience in it will be compensated by Allah in the Afterlife, which is better and more enduring. Physical affliction should not prevent one from living life, and we must be content with Allah's decree and destiny. Look to those who are below you to recognize Allah's blessings upon you. Do not despair of Allah's mercy, and if there is a cure for deformities, seek it, and adhere to supplication.