Is looking at the Mus'haf during recitation upon forgetting part of a verse considered "deceitful," and what is the remedy for obsessive fear of sinning?

Fear of committing sins is good, but one should not exaggerate it lest it lead to despair of Allah's mercy. For indeed, man is prone to error, and Allah is Forgiving, Merciful, accepting repentance. If you fall into sin, repent with sincere repentance, for he who repents from a sin is like one who has no sin. Allah Almighty says: "Indeed, those who fear Allah - when an impulse touches them from Satan, they remember [Him], and suddenly they become insightful." What you did with your shaykh, reading without memorizing, is cheating, a betrayal of trust, and adorning yourself with what you were not given. The Prophet, peace and blessings be upon him, said: "One who claims to have been given what he has not been given is like one who wears two garments of falsehood." Therefore, repent to Allah and do not repeat this act. It is better to make a mistake and have the shaykh correct you so that you may learn.