well, dd2 had been discharged from hospital with full physio and slt follow -up after spending 5 weeks in scbu after a term birth injury. they called it 'developmental delay' for nearly two years, but at 6mos had suggested we apply for dla, which was awarded at high rate.
by about 6 mos i had done enough googling
to know she obviously had cp, but no-one was mentioning it. so i waited a year and a half more before i asked the consultant what her dx was. and he said spastic quad cp.
i was, to be honest, completeley elated that finally someone had confirmed that i wasn't bonkers.
it does subside, and then you go and reread the info and start fretting about what it means, but tbh once you know what could happen, you can plan, and push for support to avoid it. and fight for what the child needs with the diagnosis in tow. labels are a great door opener.
so, dd2 has cp, and her dx is athetoid (not spastic quad now - and with cp muscle can change immeasureably over time) and she has quite low tone, with a fair amount of hypermobility. she's 8 now, and makes me laugh every day. so full of life and totally keeps me on my toes working out how she can do whatever it is she decides she wants to do next. currently she wants to learn how to rock climb.
presumably cp is your 'bad' dx? it doesn't have to be all that. 
good luck with your appointment. sometimes the worst case doesn't seem so bad once you get your head round it. be kind to yourself x