Answer
I believe that most traders lose because of trades based on emotions and they do not have a proper money management plan and understand basic concepts such as forex margin and leverage. I would not say that technical analysis does not work but i would say that it is limited in what it does. I believe to win trade the forex market one should be disciplined, well capitalized, trade longer time frames and use technical analysis with a blending of heat maps such as what Mark described above.

To learn forex margin and leverage you can go to http://www.forex-margin.net

All the best,

Amit.