I have followed this thread on and off for a while now, I just wanted to add some thoughts of my own and where I am heading. To be upfront I am neither an experienced or profitable (yet) trader but I'm only 6 months in to taking it seriously albiet part-time around the 'day job'.
I obviousl believe it can be done part-time but you have to accept that there are aspects of learning which are relative to time spent learning. Most of us learn to drive over 3-4 months, a couple of lessons a week. Some opt for 1 week full time intensive courses.
Discipline and Patience
Have a trading plan, write it down and stick to it.
Record your results, analyse if there is any reason or pattern to times you make a profit vs times you make a loss.
No trade = No loss. I've found the days I've spent 2 hours in front of Bet Angel and the TV but placed zero trades are very beneficial mentally, knowing I had a plan and nothing has met the criteria.
Understand the Risk/Reward ratio
My trading strategy is safe, low volume, high strike rate. On this basis if the price goes against me after entry then my entry was wrong and therefore I must exit. I can always enter again if my criteria is still met but this is a seperate trade. I would typically green at around 10-15% of the trade liability, my biggest mistakes are hanging in a trade thinking I have seen something and ending up with a full liability loss, this will take me 10 good trades to recover.
Use multiple indicators
If there are 2-3 justifications to enter a trade then if any one of those changes you still should be able to exit without too much impact.
Start simple and be realistic
There are a lot of people claiming there are riches to be made from trading but at the end of the day it's a job and you don't start any job with no experience on the top pay scale.
Most markets are scalable to a decent level, don't lose money learning, don't think about making money, just learn the process.
In my day job my 'saleable value', or the 'value of my intelligence' is from £30-50 per hour and thats with 20 years experience, there is no reasonable justification to say that by trading sports I should be making 6 figures a year, it might be possible some day but it isn't some magic job that's not aligned with the rest of the world.
The sport of kings.