"Edge" changes as one's knowledge changes, what I thought 39 years ago was important is not any more. If I said "it is not how much you make that is important, it is what you don't lose that is important", most would not understand but few would. And of course the masses would want me to share it, guess what, I have shared it in various posts and cause people think anything worthwhile would never be shared, laugh is on them. There been a few who have found my edge, and they have sent me letters saying so, and they were very surprised, and I have made a difference in people's lives, but people want the keys to the kingdom without working your asses off. Just cause you have the edge, you still need to make it yours so you can fully understand it. And there are many edges in trading, but people waste so much time learning about scalping and day trading, the big money has always be in long term trading, Commodity spreads, and options.
If you are working at how to lose less often than S&P Index, you will beat the Index if you catching the trendable moves of the Index and not have the same drawdowns. Keeping it simple, if the Index finishes plus 15% for the year but had a 15% drawdown on the year, it actually made 30% for lucky souls who got in trades at bottom of the drawdown. So say you cut down the drawdown by half, you will finish 22.5%.
Day trading can be very profitable, but you are going to have to be able to handle a great deal of disappointments for years for those who don't learn to program, and once you automate, there are limits of how much you can safely trade without causing your own losses and massive slippage in future markets. Stocks comes down to volume as well. Really hurting is options on stocks since more ETFs, I can see many stocks simply stop having options.