Find something you want to do, try to do it, find out what you don't know, and learn it. You could try learning from a book or a course, but personally I've ne

Find something you want to do, try to do it, find out what you don't know, and learn it. You could try learning from a book or a course, but personally I've never found a better way of learning "what I need to learn for X" than trying to do X and then googling all the things I don't know. Sure, you'll forget a whole bunch of that stuff, but if it's at all important you'll find yourself re-learning it again and again until it sticks.