Masturbation hurts in several ways:
It is a sin, is selfish in that someone else suffers because you weren't there for them, it fills your head with sinful images especially if you are viewing and revelling in someone elses sin, it saps your strength and robs your body of nutrients, it makes you appreciate your spouse less and as a sin, causes you to distance yourself from God.

If you used your strength to search for a mate, then you would be able to share sex for what it was meant for. When you masturbate, your future spouse suffers as they wait for you to get the courage to find them. When you masturbate you lower your courage and drive to go out and find your future spouse. Also, if you were meant to be single, the energy you could have used to help others is spent on yourself... but no human is perfect, nobody is without sin but Jesus and Mary. Pray for assistance and try.