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many have experienced problems like yours and to be honest, in the past, I was one of that (always lose because of selling and buying at the wrong price). this all happened because of my inability to control emotions.. my advice is to learn to control your emotions by trading small amounts every day, if you are able to control your emotions a little then you can increase the number of your transactions and so on.
Your method makes sense but very few people are going to apply it, why you may ask? Because people do not really have the patience to wait for weeks or for months to finally begin to trade their capital, they think that if they are not trading money when the market is hot then they will have to wait for months or even years for those conditions to appear again not understanding that a good trader can make money under any conditions but you can only become a good trader if you study and practice your abilities as a trader.