The first 20 hours -- how to learn anything by Josh Kaufman -https://www.youtube.com/watch?v=5MgBikgcWnY

You can be a top 10% in any given field with this. 20 hrs is worth the effort on skills you want to learn.

My personal advice - Learn only if you put that skill into use immediatly for your good or for the greater good of the society around you. Growth for the sake of growth is the mindset of a virus