How can one get rid of obsessive thoughts and anguish, and achieve trust and positive expectation of God, while the answer to prayers for marriage is delayed?

Trust in Allah and having good expectations of Him is a branch of knowing Him and believing in Him. This is achieved by contemplating the Qur'an, frequently remembering Allah with a present heart, understanding the meaning, and studying and enumerating Allah's Names and Attributes. Whoever lives within these expansive realms will find their heart expanded and their soul at peace, and they will be certain that what afflicted them was not meant to miss them, and what missed them was not meant to afflict them. The questioner is reminded of the Prophet, peace and blessings be upon him, who said: "Whoever makes the Hereafter his preoccupation, Allah will place richness in his heart, gather his affairs for him, and the world will come to him submissively. And whoever makes the world his preoccupation, Allah will place poverty between his eyes, scatter his affairs for him, and nothing of the world will come to him except what has been decreed for him."