Having worked and traded in many environments I have come to the clear conclusion that to be a successful trader, (and I do not accept that making small beer is successful) you have to get set up professionally in all aspects of what you are attempting to achieve. Half hearted and non-commitment is never a recipe for Succeess.
Trading for part timers is like grand prix driving in a mini: you might take the odd good corner, but you'll never win the race, and probably break down anyway!
I think the whole thing comes down to "its not what you do its how you do it" . that also applies to trading. You will find in every field many people involved in the same business, but only a handful make the real money, the reason is that they do what they do in a different way.
This is akin to having a good method. Many traders have a method that works for them and allows them to generate a living from the markets. They are very disciplined and follow all the rules of trading and money management. Although they have a professional approach to trading, they may not be as successful (financially)as, say a property developer, because their system generates a balanced win/loss ratio.
This trader will call himself a successful trader, he has all the attributes of a professional in his approach, just not such a robust trading system, though he still makes money trading full time.
On the other hand you have a trader who has also developed a system that allows him to buy and hold over several days. He makes far more money than the daytrader because he trades a larger size . He only trades part time but has even better returns than the property developer .
I use the above examples from reality, i know traders who are in both situations . But the point being its how you do what you do that will make a difference.
In trading this may involve trying to understand price and the markets a little more so as to develop a better system which will increase % winners.