The ibtilaa' (testing) of the believer is like medicine for him. It cures him from illness. Had the illness remained it would destroy him or diminish his reward and level (in the hereafter). The tests and the trials extract these illnesses from him and prepare him for the perfect reward and the highest of degrees (in the life to come).
Ibn Qayyim Al-JawziyyaAnd to have spent the night sleeping and awoken regretful, is better than to have spent the night standing (in prayer) and awaken impressed with oneself!
Ibn Qayyim Al-JawziyyaA true believer does not fear physical death, rather he fears the death of his heart
Ibn Qayyim Al-Jawziyya