Take A Cold Shower
This is something you can only really do if you’re at home, but it’s something you can really easily do. If you’re self-harming because you feel numb or disconnected, then taking a cold shower can help to ‘wake you up’, and make you feel something.
It’s important to find what works for you. If this doesn’t help, don’t worry. There are plenty of other ways to cope. See other ideas of things to try.