Using little capital when you start trading can't be emphasize on more as the losses that traders get starts when they began trading. If you use a small capital, you would no lose so much money when you start trading that you'll be behind and trading to makeup for your losses.
Dummy trading sounds even better than small capital, you would not be losing anything more than time and some pages if you are doing it physically and not even that if you are doing on a excel sheet.
Emotions are common when you are having money at hand and you know that you can double it or lose it all. Hence the above needs to be practiced and emotional blunted as much as possible. If you cannot do that then trading is not for you - this needs to be realized quickly by the trader.
Also you dont need to trade everyday - in fact day trading is not even recommended for anyone who is not already a day trader.
Everyone has emotions, but there are people who can control their emotions and can make them stable and there are people who can't control them which makes emotions control them. So I agree with you that someone should be able to know themselves very well so that they know whether they are capable of doing something or not. Including in trading whether they will be patient enough and can suppress emotions or they can't suppress them.
When they know what type of person they are, they should be able to understand more about what they will do, stop or continue. But they can also learn a lot to control emotions, and it is better to learn that first before entering the trade. It is better to wait longer but at that time we are really ready than to force ourselves when we are not fully ready.