It's not just the money, stupid.

Ask yourself what you need to retire (early or not). Chances are the first thing you said was "money". You're right, of course, the first thing you need is some way of surviving - some way of getting things that money can buy: food, lodging, clothes.
But, you also need things that money can't buy - or at least are probably better if not bought. You'll need to have them ready when you retire.
The earlier you plan to retire the harder it might be. All that time and effort going working towards building a big enough pot of money will make it more difficult to focus on the other sides of your life.
What to do? We'll discuss that over time. But first, and the younger you are the harder this is: think about what sort of retirement you really want. You'll only have one. It's at the time when you don't want many regrets. There's not much you can do to change things then.
You will need to build a fund to support your retirement - that fund needs to have more than money, though.