This is a very important topic you came up with. Most people know when to enter but they don't have an idea where to exit be it in profit or to stop a loss. This is a major reason as to why most traders fail in market. They get anxious and ruin their trades even when they are right.

I am a technical analyst and believes in the study of charts along with market psychology and sentiments. Combining all takes me to my exit strategy. One things i believes in most is -

"BUY ON FEAR AND SELL ON GREED".

Every investor or trader needs to understand their risk appetite and have their investment goals clear. With greater reward expectations comes greater risk. So exit strategy should consider the risk aversion of the investor.

Now like you said the percentage method, its an effective tool but it can do miracles if we combine the same with technical analysis.

Also as the crypto is the new safe heaven and a great hedging option i feel people need to understand which cryptos are really worth and which are just bubbles. The underlying asset value should be learnt and if it contributes significantly creating business value like #BTC and #ETH, i feel some portion of our investment should be held for long term in such assets.

I hope you find this useful and let me know about your thoughts on it.