I started actively trading around 5 years ago, and only picked longs another 5 years before that. It's difficult to give an exact % because I'm not a day trader per se. I trade around a position I know well, but do day trades when I spot an opportunity. Sometimes you know something will happen, but only on a short time frame.

For example, I went into oil stocks earlier this year, and I knew that the market was panicking over the low oil price. So some days the market would bounce back right when the oil pits close at 2:30 (since the oil correlation can't get much worse then). Take a chance to ride the way back up, why not? But you can't do this all the time, which is why I gave you this esoteric example.

Well, if you still want a percentage, I'd say 10-20% might be a reasonable achievement.