Why do i want to hurt myself whenever mess up?

Because whether you're conscious about it or not, you're looking for a way to punish yourself when you feel like you've messed everything up. But that's just the easy way. It's simpler to just distract yourself from your mistakes with physical pain. It took me years to face it. It's way easier to think that a new wound would make up for whatever you did wrong, but then when the scar appears, there's regret. Maybe even before that. The truth is we all mess up. Every single one of us. Nobody is perfect, and whoever you think is, had to mess up a million times to be better. And you just have to forgive yourself for your mistakes and let go of the guilt, stop blaming yourself and do something about it, stop thinking about everything you think you do wrong, be better and find a way to fix it. But then again, that is the hardest part.

That's a reason some people self harm, it could be a way for you to punish yourself and self harming is that punishment for you

The main reason why our mind goes that way is because when we are sad/depressed/anxious we look for things that are wrong to justify how we feel and when this emotion is present for a long time, at times we can’t find something to blame this feeling for so as a result we blame ourselves therefore giving birth to self hatred and vulnerability towards everything we are and when we fall down and low we try to find ways to feel okay and self harming does that for us as we are making ourselves suffer so when we feel bad, we can justify being okay by the self harm that we induce it. Hope this helped and stay safe please, get some help if you can and always remember you deserve love and happiness🌻

Because you feel guilty when you mess up and you think that you deserve to be punished for that. But that's not true, we all mess up sometimes

You could be dealing with sever depression. Try going to see a therapist to help yourself talk through what bothers you.