Depends on how you define success. For me it was being able to pay the bills, have the freedom to do as I pleased most days and know that I was in good shape financially. I started at age 40 in 1996 and have scaled back to trading less these days but it's still my sole source of income.
I started trading in 1969. I was 25. I lost almost all of my bankroll in a year. I saved more and tried again...and again. The first year I made a profit for the year was 1984 - 15 years later. Today, I make a living from trading. Nowadays, I think one could become profitable in a year or two. Markets were different then. No Internet, no interactive charts, commission $150 per trade, etc.

