Yes, we have been lucky, but humans ain't been around that long, so we huvnea witnessed the bigger impacts whose effects where global.
But oor luck wont last forever, sooner or later we will be blootered by a big wan. The ones we know aboot are should be fine, its the sleekit wans that come bowling oot the dark that will catch us oot wi oor knickers doon.
Here is one they know aboot, Asteriod 2004 NM4.
This bugger is reckoned to be a mere 1340 feet across. According to some doommongers, it was reckoned it had a 1 in 63 chance of impacting Earth on 23rd April 2029. Mibe its time to dig oot ra tin hats an dunkey jaickits an start digging.
In astronomical terms, NM4 is hardly a big object, but is bigger than the bugger that stoatit a remote area in Siberia in 1908 flattening 1000's of square miles of forest an gieing a couple o bears sair heids in the process.
Anywan starting as book on this one? A'll stick 10 slabs o McSpewans Export oan it being a dud an missing!
Black holes are where God divided by zero.