Why is self-harm so addictive?

Because the twisted chemical mess your brain is in makes it seem like what you're doing truly helps. Self-harm is usually used to gain temporary relief of some kind. When it seems to "work" for the first time, taking the pressure of your mind off the actual issue, it gets normalized by your brain; the action leading to a seemingly positive result is encouraged. You are not at fault for this, you never are. It is your brain not being able to differ between unhealthy and healthy coping. You have the power to take that differenciating into your own hands.

Because it releases endorphins, that make you feel somewhat better at the moment

I think the fact is, people do it because they feel as if they deserve it. Or everyone is against them.

It's a coping mechanism, and a form of control that become ingrained behaviour over time. Some people play with their hair for comfort, others self harm.

it is addictive because when you start doing it you feel like that is the only way to make it better

It is a type of sublimation that substitutes emotional pain for the physical. When someone is experiencing hardships or stress it can be a sort of relief to self harm, it is a temporary fix, but the problem won't go away until you find a way to deal with your problems rather than substituting.

Self-harm is very addictive being of the endorphins being released when a person cut's themselves, therefore they want too carry on which this happy feeling and as a result, cut more.

Physically, self harm produces hormones called endorphin which causes a high. This addiction can also be formed psychologically by forming a dependency on the release it causes.

when we became so sad and when we didn't find solution of our problems then people start self harming

Once you find something that gives you that temporary relief or of feeling it becomes a comfort. Bye.