Rajesh, I agree with you 100%. I have always said that trading is so open-ended as far as the individual is concerned. I'm talking about the techniques, approaches, how long someone likes to hold on to a trade, etc. There are about three things that are no room for opinion, and if you don't have them you are bound to fail in trading, and they are:
1. Methodology
2. Money management
3. Mind discipline
Having said that, when you ask about position size and money management you should use, that is a personal thing. You might like to scalp, daytrade, or even position trade. All those tenures of trades may require different size stops and even position size.
Other types of trades could have a backup plan to it. As an example someone may take a trade thinking the trade is going to go this direction today, but something happens. A look at the analysis for the bigger picture shows that market will still be there over the longer haul, so they hang on to it, and with the longer picture in view someone takes a position size in accordance with that view.
Personally, I am one to add to my position as time goes on. if it goes against me. Most people do not have the stomach to do that. This is where the full confidence in my S&R's as well as other aspects of my methodology come in at.
The one biggest trade I ever had was in the latter part of 2008. It went against me of 300 pips before it turned in my favor. When it was over, it was +2,000 pips. My position size was in accordance with my longer term view. Having said that, there are a lot of people that do not have the stomach to let a trade go over 300 pips against them.
There are some daytrades I take that I won't let it go against me 20 pips and I'll take it out.
All circumstances are different. Other trades are based strictly on a confidence factor.
Another factor is the type of accounts someone has. I view this as something that sells e-books. It is the type of account that the trader has 1000,s in another account, so he opens a separate account with $500, and in a few months grows it to $10,000 with ridiculous lot sizes and he got lucky. Yet, his main account would not have been managed nowhere nears that.
You get the picture. There are so many variables. If you are uncertain of your position size or your money management skills, but your methodology is already in place, then I would suggest to experiment on a demo account. Until you have made a conclusion, I would trade being very conservative.
Take a nerve test test. If you can't open a trade, then shut your computer down, and be perfectly calm about it, and just go on and enjoy your life, then it is either something is wrong with your methodology or your money management, which could mean stop size or position size.