The Earth is no stranger to close encounters with space rocks. Countless small asteroids are turned to smoke and dust in our atmosphere on a daily basis. Once a year or so, a car-sized asteroid might drop in and share the same fate.
The only real threat comes from asteroids and meteoroids that are a lot bigger, about the size of a football field, or even multiple football fields. A collision with these giant asteroids will, without a doubt, end badly for us. Thankfully, those events happen once in 2,000 years or so. But while these large asteroids will cause a tremendous amount of damage, humanity will still survive.
The ones you really want to watch out for are the extinction-level asteroid impacts. Space experts think they happen every few million years " give or take a few ten thousand.
Currently, we have no way of escaping an impact that powerful, but there's work being done to give us that 'planetary defence' capability.