Masturbation is only a mortal sin if you have full will. For most men, it has been something they started when they were around 12 and have been fighting it since.
By definition it is NOT a mortal sin if they have a weakened will.
You do not want to place this concept in a person’s mind (male or female) that it IS a mortal sin if they have been doing it for 20 years now and if they DO NOT STOP immediately then the next time they do it they go to hell if they die without confession. This is not theologically in line with Catholic thought, it is not charitable, and it is not common sense.
If you HATE masturbation, and you are still a slave to it - in your will (which is what fundamentally counts), you have told God that you do not want to be here. It is an addiction. However, you can be addicted to it and LOVE it - therefore in your will you have consented. Your body may be addicted to something, but the faculty of the intellect, that which makes us in the likeness of God, will must also have consented to make it a mortal sin.
I will repeat, if you have not consented in your will - it is not a mortal sin; translation do you ENJOY what you are doing? If you could push a button to stop immediately, would you do it and rejoice? Do you HATE masturbation?
Matthew 26:41
God Bless you.