How can one return to commitment after backsliding and committing sins, and what is the way to overcome the feeling that God has cast the questioner out of His mercy and that there is no repentance for his deed?

You must hasten to sincere repentance to Allah and abandon the feeling of despair from Allah's mercy, for it is from the whispers of Satan. Allah accepts the repentance of those who repent, no matter how great their sins, and replaces their evil deeds with good deeds for whoever repents, believes, and does righteous deeds. To achieve this, one must abandon sins, distance themselves from bad companions, maintain congregational prayers, associate with the righteous, and recite and ponder the Quran.