There are a bunch of people who spend their entire working life looking for and at these things. I've met one of them.
The scary possibility is that something could come from us more or less from the sun, and we would not see it until right before the impact. The 2013 event in Siberia was one such.
The Tunguska meteor was incredibly devastating, although I have no idea if it was seen or tracked before it grazed our planet. That's not the kind of thing astronomers were looking for back then, so I just don't know.
Meanwhile, a lot of folks are looking at and for potential meteor strikes, and so far we seem to be quite safe, although it is inevitable that some major one will hit eventually.
65 million years ago a 10 mile in diameter asteroid crashed into our planet, making the Chicxulub crater and killing off dinosaurs. Perhaps at some point something similar could happen, kill off most of us, and resetting life on this planet. Somewhat like The Big One, meaning the major devastating earthquake in California is inevitable, something like that asteroid is probably inevitable also, although on a vastly different time scale than The Big One.
Me, I'm an optimist.
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Thanks. I needed a good laugh. 
