Being focused at 21 is way over rated. Now is the time to screw up, try as many different things as you can and just maybe figure things out.
The thing you do need to do is learn. Learn accounting. Learn finance. Learn statistics. Learn as much as you can about business. Read biographies about business people. You dont have to focus on 1 thing, but you have to create a base of knowledge so you are ready when its time.
You will never know when that time will come. But you can be ready when it does.
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