Is anxiety and fear concerning the non-acceptance of repentance, or God's displeasure, or excessive contemplation of such matters, considered despair and hopelessness regarding God's mercy, and does it necessitate sin?

A person afflicted with obsessive thoughts (waswasa) must disregard these thoughts and not succumb to Satan by dwelling on them. They must know that Allah is All-Forgiving, Most Merciful, accepting the repentance of those who sincerely repent, as He said: "And indeed, I am the All-Forgiving to whoever repents, believes, and does righteousness, and then is guided." The cure is to completely turn away from thinking about these matters and to occupy oneself with learning, inviting to Allah, programming a schedule for memorizing the Quran, learning jurisprudential matters, reading books of biography, and being cautious of isolating oneself.