Bitcoin has a long history of steep dips, yet it has always gone higher. I think it is prudent to never sell below ATH.
Same applies to Monero of course.
Don't invest in BTC/XMR any money that you cannot lose. And sell so much in the tops that you can take the dips to zero if need be, without getting tempted to sell at the bottom.
From the Zurich Axioms; Minor Axiom I
Always play for meaningful stakes.
"Only bet what you can afford to lose," says the old bromide. You hear it in Las
Vegas, on Wall Street, and wherever people risk money to get more money. You read
it in books of investment and money-management advice by conventional counselors
like Sylvia Porter. It is repeated so often and in so many places that it has taken on
an aura of truth through assertion -- just like the shrinks' bromide about getting
calm.
But you should study it with the greatest care before making it a part of your
speculative toolkit. As most people interpret it, it is a formula that almost assures
poor results.
What is an amount that you can "afford to lose"? Most would define it as "an amount
which, if I lose it, won't hurt." Or "an amount which, if I lose it, won't make any
significant difference in my general financial well-being." A buck or two, in other
words. Twenty bucks. A few hundred. These are the kinds of amounts most middleclass
people would consider loss-affordable. And as a result, these are the kinds of
amounts most middle-class people speculate with, if they speculate at all.
But consider this. If you bet $100 and double your money, you're still poor.
The only way to beat the system is to play for meaningful stakes. This doesn't mean
you should bet amounts whose loss would bankrupt you. You've got to pay the rent
and feed the kids, after all. But it does mean you must get over the fear of being
hurt.
If an amount is so small that its loss won't make any significant difference, then it
isn't likely to bring you any significant gain either. The only way to win a big payoff
from a small wager is to go for a long, long shot. You might buy a $1 lottery ticket
and win a million, for instance. That is nice to dream about, but the odds against you,
of course, are depressingly high.
In the normal course of speculative play, you must start out with a willingness to be
hurt, if only slightly. Bet amounts that worry you, if only a little.