This saying was made popular by Larry the Cable Guy who was the voice of Mater in the cartoon movie Cars. I can still hear Mater saying it.
It symbolizes taking action, eliminating procrastination, overcoming what might seem to be insurmountable obstacles as well as all of people who tell us regularly that it either can't be done or is not worth the effort. At its basis is a positive can do attitude.
Our country was built on people who truly believed in what they were doing and did whatever it took to get it done. This same motivation has driven many seemingly insignificant people to accomplish great things and produce revolutionary products such as the automobile, airplane, light bulb and the internet. All took, not only a vision of what could be, but the drive to Get-Er-Done and make things happen.
What is it that you believe needs to be done? What is it that you have been putting off to a better time? Time is ticking by. Let's not be the little old lady I remember who often said in her older years" "If only I had - - - ." We all have significantly more talent and ability than we give ourselves credit for. It is up to each of us to rise above those seemingly insurmountable obstacles and "Git -Er-Done!"