Success:
-Financial => Financial freedom via real estate or any other business
-Happiness => Being able to do that which makes me happy instead of that which makes me money
For me success means not having to trudge into work to do something I hate to make money. I also enjoy helping to educate others toward this goal too so success is making my students successful.
I think people are very bad at setting the RIGHT goals that take into account what will make them happy. Simply having more for more's sake is stupid unless the incremental effort is worth the cost. Everything in life is a tradeoff. The only thing you can never get back is your time.
John T. Reed has a book called "Succeeding" which is worth the cost and the time invested if you want to get a crystal clear vision on success. You can hit the highlights by going to his site, clicking on the title, and looking at the outline and the copy he uses to sell the book.
Personally, I have always felt that happiness is a choice. There are people that are very happy in what many of us would call miserable situations. Others that are far from being happy though financially they are very well off.
I happen to enjoy real estate investing and enjoy the interaction with people and the brainstorming which is often apart of a new investment. I enjoy taking a property that was a good investment and turning it into something of greater value. Perhaps that's why I look for that added potential in every property that I buy. To me it is not enough that an investment be good, there also must be some hint that it can be much better.