What has often worked for me is to get involved in something kinesthetic, i.e., doing something that requires movement. For me it's doing something with my hands; creating a project of some kind. It doesn't work 100% perfectly but it IS a great help. If unwanted thoughts start to creep in again, just need to refocus on what you are doing.

I'd be careful of the "rubberband trick." Some self harmers use it to do some form of self harm with it.