being greedy isn't good especially doing trading 'cause you will end up to regrets and losing money, so first thing first if you want to earn profits, learn first to control your emotions before jumping into it and to avoid loses and etc 'cause that's the common reason why people always panic when there's a fluctuation in the market.
Anyone who is greedy while trading will most of the time always would not know when to be selling and usually do not always have a plan and a strategy, What makes professional traders is not by trying to get the best value to sell, it is by having a plan and sticking to it, irrespective of what the market eventually gives. Yes, as much as one may have strategy to buy, it is always necessary to know what to look out for to sell in a market depending on one's trading pattern.
Your point here is a final one that anyone that wants to increase in trading faster should adopt even though it can be very difficult but when enhanced can be very helpful.