To be honest, I should be the one double face palming here. Promoting worldly wisdom over godly wisdom? I speak of this because it is a real issue for myself and I have done the research. And the harm is predominantly spiritual, best believe it is sin and it will undoubtedly harm your walk with God. Yet you dub it as "having a weak heart", which couldn't be further from the truth. If having a "strong heart" means being able to sin without experiencing serious repurcussions on the conscious, I'd say there is serious work to be done. I came across an excellent post on the topic from a user on another site...
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Though sexual offenses such as premarital sex (fornication), homosexuality, adultery, and inappropriate behavior with animals are plainly condemned as gross sins in the Bible, masturbation is not mentioned. (Genesis 39:7-9; Leviticus 18:20, 22, 23; 1 Corinthians 6:9, 10)
Masturbation was common in the Greek-speaking world during Bible times, and several Greek words were used to describe the practice. Interestingly, not one of these words is used in the Bible. Since masturbation is not directly condemned in the Bible, does this mean it is harmless? Absolutely not! Even those not especially concerned with God's viewpoint feel uneasy about the practice. For instance, Dr. Aaron Hass in his survey of the sexual practices of 625 teenagers reported: The majority of adolescents who masturbated reported feeling guilty, ashamed, dirty, stupid, embarrassed, or abnormal. Surely, masturbation is an unclean habit. But since uncleanness, according to the Bible, is a term that allows for a wide range of degree of seriousness, masturbation is not to be classed with such serious sins as fornication or other types of gross sexual immorality.Ephesians 4:19. Masturbation also instills certain attitudes that are mentally corrupting. (Compare 2 Corinthians 11:3.)
This habit teaches one to treat his or her body as merely an object to be used for sexual pleasure. When masturbating, a person is immersed in his or her own bodily sensations, totally self-centered. Sex becomes separated from love and is relegated to a reflex that releases tension. But God intended sexual desires to be satisfied in sexual relations, an expression of love between a man and his wife.Proverbs 5:15-19.
Losing this viewpoint can lead to problems in adjusting to a right relationship with those of the opposite sex. Such ones could be viewed as sex objects rather than as sensitive human beings. One may tend to exploit another as a mere tool for sexual satisfaction. Such wrong attitudes taught by masturbation can defile one's spirit, or dominant mental inclination.
For good reason, God's Word urges: Beloved ones, let us cleanse ourselves of every defilement of flesh and spirit. (2 Corinthians 7:1)
How to fight it?
The battle against masturbation is fought in our mind. Hence, the Bible recommends: Prepare your minds for action; be self-controlled. (1 Peter 1:13, New International Version) For instance, we may happen to notice something that is sexually stimulating. The mind is inclined to dwell on such thoughts and let passion develop. (Matthew 5:28) When that occurs, our bodies tend toward sexual activity. The longer our minds dwell on the wrong thought, the more this physical process escalates to higher phases of excitement. Eventually, the level of arousal may lead to masturbation. But the mind must exert itself and reject the immoral thought. If it does so, then the arousal soon dies down and any discomfort because of body tension fades.
When you have difficulty falling asleep, endeavor to imitate faithful King David, who wrote: When I have remembered you [God] upon my lounge, during the night watches I meditate on you. (Psalm 63:6) Forcing our minds to ponder on God and his qualities will often break the spell. You lovers of Jehovah, hate what is bad, wrote the psalmist. (Psalm 97:10) It is not easy to hate a practice that brings such momentary fleshly pleasure, but keep thinking of how God views this unclean habit
Avoid like the plague any reading matter, TV programs, or movies with sensuous themes. Don't keep looking at such things. Make my eyes pass on from seeing what is worthless, prayed the psalmist. (Psalm 119:37) Such sights will be stored in your mind and often resurface when you are alone.
Finally, to assist in maintaining self-control during the nighttime, one Christian advises: Before going to bed, read something related to spiritual things. It is very important that the last thought of the day be a spiritual one. Prayer at this time is also extremely helpful.
Sources: The scriptures cited and the publication, The Awake! Magazine, March 8th 1988, page21
Watchtower Bible and Tract Society