The first thing to understand about self-injury is that normally it is not an indication that the injurer wants to kill themselves. In fact, usually just the opposite is true. No one can doubt that some self-injurers are suicidal, but that is far from typical. People who cut are trying to avoid unwanted feelings or thoughts, like suicidal thoughts and feelings. They want to be numb in much the same way a drug addict wants to be numb from the rest of their lives.
One very important step on the road to recovery is recognizing that you no longer want to cut yourself. It may sound easy, but it is a complicated process. There will be a part of your brain that wants desperately to stop what you know is a destructive behavior, but the rest of you will be aching to pick up that razor just one more time. Whether you believe it or not cutting is a highly addictive behavior and can be the only way one knows how to cope with stress or emotion. I do not say this from the position of a mental health professional, or a by standing friend or family member, I speak from experience. Having spent most of my life in the grips of my own cutting, I know how difficult it can be. But it is not impossible; you can overcome your cutting and stop if you really want to. Recognizing that there is a problem and that this is an addictive behavior is the first stop on that journey.
Next it's important to find someone you trust that you can discuss your feelings with. This can be a therapist, a priest, a parent, a sibling, or a friend. This is probably one of the hardest steps; chances are you've been hiding your cutting from the world for a long time. Don't be discouraged if they react badly, it's natural for them to be shocked and concerned. But running from your feelings and emotions has led you to cutting; you need to give yourself another outlet for those emotions than on your skin. Talk to the person you trust when you feel the desire to hurt yourself. You will need their support in the early stages of recovery, so don't be afraid to tell them about your urges to cut. They may be able to provide you a distraction that will keep you safe.
It is also advisable to remove your "kit" from your immediate area. I'm sure you have all your cutting tools set aside somewhere just in case, I know I always did. Think about it this way, if you have to search for something to cut yourself with you are more likely to calm down and no longer want to once you find something. It has probably become such a habit to go to your kit and cut, that if you have the time to think while searching for something the desire may pass.
You should identify the triggers that cause the urge to cut. The very moment you have the desire to cut stop and think about what has just happened. What was it that made you go to that place? Was it a feeling that caused the urge? Was it an action that you or someone else had taken? Once you identify it you can try and eliminate this trigger from your life until it no longer causes you to feel that cutting is the necessary outlet.
Distractions are also a great way to stop cutting in the early stages. You will still want to feel that pain early on, so hurt yourself in a less harmful way. Wear a rubber band around your wrist and snap yourself with it when you feel like cutting. Or hold an ice cube to your skin for a minute or two. These things will cause pain but are less harmful in the long run. You can also draw on your skin with a red pen if you wish, to simulate blood. Other distractions can be helpful in expressing your emotions as well. Draw, paint, listen to music, write a poem, go for a run, or take the dog for a walk.
Try and relax when you feel the urge to cut. If you're like me then you feel anxious and stressed right before you cut yourself. Try taking a deep breath and just tell yourself that you are not going to cut because you are strong and will stay safe. Close your eyes and just breathe for a few minutes. If that still fails, never underestimate the power of screaming. Stand in the middle of the room (provided that the neighbors will not end up calling the police) and scream at the top of your lungs. Shout out loud what is causing you to want to cut, or what is bothering you.
It is also important to love yourself. I realize this can be the hardest part, feeling worthless and small is a large part of cutting. I know you don't feel like you are worth it, that you do not deserve anyone's help or attention. But you do, and you can live a safer and happier life if you choose to. Think about it this way, if you love someone else you would do anything to avoid hurting them. You deserve the same consideration from yourself. If you need it, get professional therapy or advice from a religious leader. Love yourself enough to not harm yourself anymore. It won't be easy, but it will be worth it. Stay strong, stay safe, and you can have a future with no new scars.