The key for me is to wait long enough before cutting until I care more about my reasons not to do it than I do about wanting to do it. Until then, it's really a matter of waiting as long as it takes - hours, minutes, days, etc. - just a little at a time until you're there. Emotions come and go and get stronger and subside like waves. You can observe them without doing anything. Distraction techniques are good for getting through when you're trying to wait, and it's hard.

Here's a list of ideas grouped by what you need (such as if you are feeling angry, or feeling sad, or feeling dissociated, or wanting to rant, or wanting to see blood, ...)
http://www.dbtselfhelp.com/html/panic_list.html