There are a few reasons for me but I think the biggest reason for me to stop was the risks of it, I may not have intended to end things but it could've happened due to either the extent of the injury or the resulting infections and there were longer term effects of the injuries such as itching, scarring and possible mobility issues depending on what and where the injury was. While it started off fairly minor and wasn't much of a problem it did escalate to the point where it became life threatening at times. A life revolving around A&E, b**n units, dressing changes and the like isn't a great life to be honest.
Another factor was that by self harming I wasn't dealing with the emotions properly and it was doing little to help in the long term regardless of severity. As I got older I never learned to cope with various aspects of life such as work, relationships, bereavement etc and I just relied on self harm more and more which is likely why it escalated to the extend that it did. I'm gradually gaining better function in these areas of life by learning to understand and deal with emotions effectively rather than just suppressing them through self harm.
I think that while it could appear as a positive or helpful thing it's usually a symptom of other issues or illnesses which will need to be addressed. It's not an easy process and will need professional intervention and when you start that process is, of course, up to you. I will say that if you are going to be self harming keep it safe; minimise the damage, keep it clean, keep first aid supplies, keep emergency money for late night hospital trips and get medical attention when you need it.