I want to also add one more point that I forgot to mention. My opinion is that with trading, the potential upside is probably greater than in many other businesses.
For example, if you open up a grocery store, you may eventually be able to start a franchise and get big like Gristedes. But you're going to have to involve a lot of people and manage them. You'll have to get investors, marketing people, managers, etc. If you like doing that kind of work and get a thrill out of such a challenge, you'll be able to do well if luck is also on your side.
Now, if you're good at trading, and you like what you do, you can turn relatively small sums into very large sums. Of course at a certain point, you will have a problem trading without moving the market, so new challenges come into play (just as with starting a grocery franchise you might say, versus a corner store). Just as with other entrepreneurs, you have to risk and take chances, hold through bad periods, etc. But you can get to that point on your own potentially. You don't need to get partners or investors or anything like that.
I would argue that with trading, the potential for upside is greater than in a lot of businesses as far as what one single person can do.
Then again, a fair counterargument is that just as few grocery store owners have the vision, energy, patience, and skills to turn a grocery store into a national franchise, few traders have what it takes to be the next Richard Dennis.
Its hard to argue with statistics either way, but in the end it comes down to doing what you can do best to make money. If you're good at trading, its better for you to make your money doing that than trying to start a grocery franchise, and vice versa.