The line, originally coined by Grace Hopper (a badass in her own right) may get overused a bit (guilty), but its merit can not be overstated. Almost anything worth doing will come with a naysayer or two, and if you go around asking people for permission it won’t be long before you find someone who will tell you no.
I’m not advocating that you go around telling everyone to fuck off. But if you really want something, sometimes you are going to have to go get it rather than asking around to make sure whatever it is is also OK with your boss, wife, parents, friends, etc.
Normal people spend too much time looking for reasons not to do something extraordinary. But then again, Normal Sucks. Go do something awesome, it might irk people a little bit. You might even get fired, kicked out, whatever. But isn’t that kind of exciting to begin with?