Take your time. If you aren't ready to have it done tomorrow, that's okay, it's entirely your decision, and you're in control of the situation. I'm not surprised you don't want it done, smear tests are really horrible, it always makes me laugh when people call them, 'quick and painless', they're painful, invasive, and the wait for the results is terrifying. Unfortunately though, we're all supposed to just get on with it. You coped the last time, though, and you coped with the puncture skin biopsy, too, so you can do this!
Try taking some rescue remedy and some painkillers beforehand if you decide to go ahead with it, and remember to tell the doctor/nurse the minute you feel uncomfortable. If it comes back as 'abnormal cells' again, make an appointment with your GP and discuss it, he/she should be able to put your mind at rest. A lot of smears come back as abnormal, yet the majority are nothing to worry about.