As a 5 years of experience i tried every method for waiting optimal profit. Waiting just with a hold of any coin is not very good at short and mid-term time intervals. Generally holders wait for historical rise but it comes in 3-4 years or maybe more. So even if you wait for that rise you can gain something on short and mid-term time. Basically i assume you have some coin just sell some of them on a small rise period, price is moving with 6k-8k for a few month so when you see 7-8k prices start to sell dont sell all but some of them should be great. Even if it rises after you sell you are now waiting it to fall , and short time period it always falls just wait 1-2 months low and buy even if it drops more you basically gained profit. So if you can read some trend moves you can invest mid-term so you dont have to hold for years. If price starts to rise historically then it is time to buy.
It is so true that even if the new ICO coin is having very promising projects you should book profit on any time as you can see when market go for correction then all coins will come down even who are having good project. So it is always wise decision to sell in profit and hold it in bitcoin or fiat currency so that you should be in position to buy back the good coins in low and do trading this way.