Although, you won’t hear many sermons condemning the practice, the Catholic Church still officially teaches that masturbation is sinful. In spite of all the pro-masturbation propaganda in our culture, "self abuse" is one of the most frequently confessed sins in the confessional. So, obviously, many people still feel guilty about doing it. Some might argue that instead of teaching people that masturbation is evil, we need to do a better job telling them that it’s perfectly okay. I beg to differ.
Many will say that masturbation is "normal." While it’s true that masturbation is very common, especially among young males, we innately sense that there’s something wrong with it. It is generally done secretly, not readily admitted to, and carries a certain degree of shame. On a purely philosophical level, you might argue that there’s absolutely nothing wrong with it; however, think of someone you deeply respect and admire. How would you feel about them if you caught them in "the act?"
Some will argue that masturbation is not physically harmful. Strictly speaking that’s true; however, why do coaches and trainers often caution athletes about indulging in sex before major events? Frequent masturbation seems to lower physical strength and endurance. (So does frequent sexual intercourse, but masturbating is usually so much easier to do.) This condition is, of course, not permanent. If one abstains long enough, energy levels rebound. The problem is that it is very difficult for many people to quit or even cut down on masturbating.
This leads to one of the biggest problems concerning masturbation: It is addictive. If you disagree, and you are a masturbator, see if you can abstain for even a month. Maybe you can, however, millions of people cannot. Many people are so accustomed to self-stimulation that they have trouble engaging in sexual intercourse. Masturbation is a lonely, self-centered practice. It encourages a self-focused, lazy attitude.
It’s so much easier to eat a chocolate donut than get up at 7 a.m. on a cold winter morning and go jogging. It’s so much easier to vegetate in front of the TV than to wash the car or mow the lawn. It’s so much easier to put off the hard stuff we know we should be doing, watch a porno movie, and masturbate! Masturbation inhibits our desire and ability to improve our selves. And, yet, even this is not its worst consequence.
Sinful, perverse thoughts almost always accompany masturbation. Through them, the spirit cooperates with the body in sin and takes delight in it. The soul then, partially or wholly, separates itself from God. Now, not all instances of masturbation are equally grave. The more intentional the practice, the worse it is. It is less evil when, in spite of making every effort, one occasionally "breaks down" and engages in it, and far more evil when one does nothing to try to avoid it but rather welcomes every opportunity – especially when one understands just how bad it is.
God is not harsh. He understands how weak we are and how easily we fall into sin. He knows how difficult it is to be chaste, especially when we are young and unmarried. Nevertheless, He demands that we make every effort to avoid sin and strive for holiness. We must strive to crucify the flesh, if we wish to enter into the joy of heaven.