I think we should keep it because our world is changing with technology. Certainly, the cryptos market will grow strongly in the future. Why not wait 3 more years? Why do not want high profits?
If you sell now, later on, you will regret why you did not keep it.
Advising to hold a long time, many don't consider the current needs of people for money. "Hold now and get profit in three years", - this council is good for those who has a passive which it would be desirable to increase. Regularly to earn money - it is necessary to trade, using volatility of the market.
That's why they must consider investing only on those coins which can give you passive income. I just get more than 1 ethereum in a month from my passive income through investing my amount in the POS coin. This works very well for me.
Stop investing in those coins which give you nothing for your investment and that's it.