Explanation:
Let us understand the term deeply,
Upgrading - Updating yourself with the latest
Retraining - learning new skills
Let me give you a real-life example which is nothing but "mobiles". If you are not updated then:
These could be done in one touch if you have latest mobile with necessary applications.
In a similar way, we need to get retrained to get to learn new skills, technologies so that we can do our job the best, to be on track, be productive, convert your valuable knowledge in terms of money, to be peaceful in day today transactions, etc.