Sin is like a foul-smelling swamp full of sewage; the more one sinks into it, the less he senses its smell, because he actually loses his sense of smell and can't tell that he is drowning anymore.
At the same time, anytime one makes a strong decision to return from this swamp, it is considered a victory. One who has decided to fight sin, needs to increase his ambitions for such, so that he can be victorious in the following stages of this struggle.
As for how to increase ambition and motivation and finally keep away from sins, there are some methods that might be useful:
1- Paying attention to the disadvantages and harms of the sin
2- Paying attention to the high value of your own character and personality
3- Paying attention to the magnanimous rank of Allah (swt) and that He has to be obeyed
4- Paying attention to the significance of struggling against sin and one’s illegitimate desires as a skill, and the pleasure of winning the struggle against the self or the carnal desires.
One of the most important points concerning this matter is for you not to lose hope in Allah’s (swt) mercy, and to trust in and ask Him for help. No matter how great the sin may be, one should never lose hope in Allah’s mercy.  He should not get frustrated even if he repeatedly breaks his repentance, and he should make up his mind and decide not to commit this sin again. We believe that you will be victorious, with the help of God and His grace.
Istimna or self – satisfaction that has been referred to as masturbation in religious and jurisprudential parlance, means doing something to discharge the sperm from the body. This can be done by touching your body, watching sexual scenes (pictures, movies, …) or reading sexual contents and books (stories, novels,…) or listening to sexual materials (tape, telephone conversation,…) or thinking about sexual matters in order to discharge the sperms. In either ways, this is haram and considered as a major sin.[1]
The best way to avoid masturbation and self – satisfaction is legal marriage (permanently or temporarily) under special conditions stipulated in practical article. If marriage is not possible, one can use the following recommendations while trusting in God and consigning his matters to Him:
1 – Decide firmly to avoid masturbation
2 – Avoid watching any type of pictures and movies sexual in nature.
3 – Be careful when you choose your friend. Do not choose the type of people who enforce you to do this. Also, avoid making friend illegally with opposite sex.
4 – Avoid dreaming and try to make yourself busy with good things such as reading books (non-sexual ones), heavy exercise, etc. Moreover, remember that idleness can lead you to anything.
5 – If possible, try not to be alone anywhere.
6 – Fasting can be quite helpful in controlling your internal desires and strengthening your will.
If you cannot fast, do not eat a lot or at least do not over load your stomach when you want to sleep.
7 – Do not eat food items, which are sexually arousing like banana, chocolate, fig, date, onion, pepper, egg, red meat, oily foods, etc.
8 – Keep your urinary bladder empty at all times.
9 – Read some books before going to sleep at night and never sleep on your front or stomach.
The conclusion is that masturbation is not permissible under any circumstances. You should take action for marriage. Fasting, studying, taking exercise and thinking about your own personality as a respected human being can help you stay away from sexual sins. Keep in touch with faithful and practicing Muslims. Surely, you should also stay away from sexually exciting and provocative things or going to such places where you might be excited sexually. If you put these into practice, you will succeed in guarding yourself against the evil of sin.

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