Once upon a time, people could earn their living throughout their lives with just one skill. For instance, if someone is a farmer, he can do farming with same methods all his life and he would do great. However, now-a-days, even farming needs upgradation in skills.
With constantly changing world, it is immensely important keep learning new skills. More important is to unlearn the redundant ones and re-learn them with the upgradation. The fast moving world is keeping everyone on their toes.
There is simple example of one’s mobile phones, every now and then there is a new version of the operating system. The version we were using 2 years back, is now redundant and the new applications don’t run on it anymore.
Change is the only constant.
Keep hustling.
Have a great day!
PC: wired.com
Walking Dead 
True