I've been doing that with Japanese shares, simply by having a core long position in Nikkei futures and then increasing my position by buying the fucking dip and selling that a few hundred points higher, repeat.
When asked about his opinion of day traders some years ago, Paul Tudor Jones replied "95% losers".
Let's say there's 50 winning day traders here :D .
That would imply there is 950(!) losing day traders here.
Think about it.
A bad trader doesn't take profits when his target is hit. OTOH, an exceptional trader "knows"* when to hold his trade for bigger gains.
*through experience and observation