They are lying because you've never made money daytrading? As per my other comment, this is absurd. Being a profitable daytrader is very hard, and it's not probable, but definitely possible.
The research in the paper suggests that the probability that your friends are making more than a teller is 0.4%, therefore the probability that they are making less than a teller is 99.6%. So, if you have a hundred friends in daytrading, only one of them made more than minimum wage, two of them made money but at or below minimum wage, and ninety-seven of them lost money. Therefore, if they all told you they were making money, most (97%) of them were lying.
Just this year, I am at 35% returns, however, September is not in my calculation and this month was probably the most profitable so I should be around 50% at the end of the month if not higher (and this is a bad year.) Also the market has been choppy lately, the last few months so harder to lock in gains.