Dear Ethan, 

First let us see if the advice your friend got is what the Church teaches, and then we'll touch on some practical tips. 

The Catechism (in #2352) tells us, "Church teaching and the moral sense of the faithful (for example, you still feel it is wrong when you do it despite what your friend told you) have been in no doubt and have firmly maintained that masturbation is an intrinsically and gravely disordered action. The deliberate use of the sexual faculty, for whatever reason, outside of marriage is essentially contrary to its purpose." 

This means that masturbation in itself is matter for a mortal sin. But for a mortal sin as well as grave matter you need full knowledge and full consent. The Catechism goes onto say that in order to judge the individual's moral responsibility (and therefore the gravity of the sin he commits), "one must take into account the affective immaturity, force of acquired habit, conditions of anxiety, or other psychological or social factors that lessen or even extenuate moral culpability." 

So, where do you go from here? First of all you should realize that in your case you have two great pluses. One, your conscience works - you know what is right and what is wrong, and you are making no excuses for yourself; two, you want to change. Very important. 

Secondly, you have to realize that you are fighting against a habit that is linked to deep and primary instincts that are part of our human nature. So it is not going to be a snap to turn things around, it is going to take patience - not a passive patience, but a willingness to work knowing that progress may take longer than you would like. In a sense you are rebuilding who you are. 

Thirdly, you have look at the beauty of what you want to be. Whether God wants you to be a husband and father or a priest, you want to be pure, in control of yourself, able to give yourself totally and be the best you can be for the person or Person in your life. Keep the ideal in mind. Work towards it: a strong, faithful husband and father; or a strong, faithful priest. 

Now for some practical aids. Very often a boy is already in the habit of masturbating before he realizes it is wrong, so he has a habit to overcome. You get into a habit by repeating certain actions; you get out of a habit by substituting others. The frustrating thing about habits is that we do them without thinking, and by the time we realize we have already done what we wanted to avoid - like someone who has a tick they want to change, it never happens overnight. Every time you catch yourself before you fall into it, every time you avoid it, you are one more step towards forming the new habit you want of purity and control. You have to think more about these small positive steps than about your failings. 

So, by doing this you begin to reduce the frequency of your failings. Coupled with this you have to make sure to reduce whatever might stimulate your passions (what you read and look at, what you speak about with friends, what you think about). 

And you have to make sure you don't become obsessed with the problem. Learn to brush off temptation, to put your mind to other things; make sure your life is healthy, with enough exercise and good friendships. Don't do things that will favor depression. 

Especially make sure to ask God's help. Use the sacrament of reconciliation, go to Mass and Communion often, pray to Mary, and especially try to get to know Christ. 

God bless.