After being afflicted with diseases of the heart and weakness of faith, is the feeling of despair from returning to God and the burden of righteous deeds considered to be a case of "But God disliked their setting forth, so He kept them back"?

Guidance is in the hands of Allah, so do not despair of His mercy. Turn to Him, the Almighty, supplicating and persisting, for He is the turner of hearts. Strive against your lower self by performing good deeds, fulfilling obligatory acts and supererogatory ones, and be keen on seeking knowledge and accompanying the righteous. When you are sincere in your striving against yourself, Allah will assist you and grant you success, as He says: "And those who strive for Us - We will surely guide them to Our ways." (29:69). Repent with sincere repentance, for repentance erases what came before it. No matter how great the sin, Allah's forgiveness is greater, in accordance with His saying: "Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."" (39:53). Ask Him for the soundness of your heart and for assistance in doing good.