"If you repent then break your repentance by returning to sin, then rush back to repentance. Say to yourself, 'Perhaps I will die before returning to sin this time.' Similarly, do this a third and fourth time. Just as you have made sin and returning to it a profession, make repentance and returning to it a profession. Do not be more incapable of repentance than you are of sin, nor lose hope, and do not let the Shaytan use this to prevent you from repenting. For indeed it is a sign of good. Did you not hear his [the Prophet's] (Allah bless and grant him peace) saying, 'The best of you are every one who is often tried and often penitent.' Which means they are often tried by sin and repent much and return to Allah (Transcendent and Exalted is He) with remorse and seeking forgiveness. Remember the saying of Allah (Most high): 'And he who does evil or wrongs himself, then seeks forgiveness from Allah, he will find Allah Very Forgiving, Merciful.'[4:110]" 
And Allah knows best and He alone gives success (tawfiq).
 Muhammad Bin Muhammad al-Ghazali, Minhaj al-'Abidin Ila Jannah Rabbi al-'Alamin (Damascus, al-Dar al-Dimashqiyyah, 1422 A.H.), pp.31-32.