I think the saying "I've lost enough today, I call it quits" is better than "I've made enough today..." Why would you put a limit to how much money you make?
To avoid giving it back. I've lost track of how many examples I've heard of people making good coin in the morning and giving it all back in the afternoon.
Why take a chance of turning a good winning day into a losing day. When I first started trading full time I felt I "needed" to be at the office the entire day, trading all day. I think it was from putting in full days in the corporate world. I can recall a number of days where I might be up $1500 or so in the first hour. Rather than quit, head home to enjoy the day I'd keep trading, and often gave back most of my gains. Finally the guy who owned the office suggested if I had a target goal and I hit it (whether it be at 10:00 am or 3:30 pm) that I head home. I took the advice.
with a decent method which thoroughly paper test, 2K should be a plenty, without any method, learn as you go as much as you can get your hand on and then some.
And that's why your co-worker friend will never be a good trader. Because he doesn't understand what trading is all about. IMHO, every new trader should read Trading in the Zone by Mark Douglas.
I started trading with 25k, and 1 years worth of living expenses. I lost half my account before I turned it around and started to make money, it took 3 months to lose that much, then I made it back within 1 1/2 months. I have had a few set backs along the way but I have always persevered. I put in alot of 18 hour days studying and trying to figure out this game, and in the end it paid off. To succeed you must have a passion for this business and be willing to work hard, learn from your mistakes. The pay off is there, nothing better than making money and being in control of your schedule.
A rough rule of thumb 50% returns a year are realistic in this business. So you want to make 50K a year (before tax) then you need atleast 100K. Ofcourse you could try to make 50K from 50K instead and use margin but then the drawdowns will feel worse (even though $ wise they are no different).