I believe that having additional passive income, apart from day trading, makes it easier to trade with discipline.
One of my passive incomes is derived from longer term trading using options. I call this passive as I don't need to pay much attention to these trades once they are on as I have both targets and stops worked out and I get an alarm when the underlying hits one of those areas and I can then take action. Apart from that I look at my longer term stuff every morning, even when I am traveling as I can do that from my iPhone or iPad. Having this passive income is not only a financial benefit but a psychological one. I did have investments in other businesses in the past but they became too distracting and time consuming, so all my investments are now either property or market oriented.
Today the London morning started off slowly until some German numbers knocked the stock indexes down. It was hard to be on the initial down move but there was enough follow through to "make a quid". The DAX chart shows the trades.