One of the best feelings as a crypto lover and holder is to see your holdings rise and increase in price while your portfolio is swelling up. But majority of people are carried away with the joy and gladness of this market pumps and then keep waiting to take profit at the peak till it begins to dip and they sell way lower than what they should have gained. It's something that's common to almost all traders. I can say greed is part of it. How do you think this problem can be solved.?
It can't be solved!
Greed is something intrinsic to human nature, and it is extremely difficult, yet not impossible to control. Once some sort of control is possible, then a remedy for trying to sell at the right times to maximize profit is unfortunately experience.
With experience, and after getting burnt several times your risk-adversity changes, and only then you're able to start devising a strategy that works for you. Like as soon as you're taking 20% profit of your investment you'll be happy or something similar.
In fact it can and you gave the solution yourself, you need a strategy that tells you exactly when to get out, one way is to do it as you state, you determine a percentage that you want to obtain out of each trade and then once that is reached you sell regardless of anything else, another way is to have a moving stop loss, basically you wait until the price faces a correction of a certain percentage until you sell, this method has the advantage that it keeps you in the market in the case of a strong bull run and it improves your profits.