Don't listen to your emotions, listen to your reason.
Let's say Bitcoin is worthless:
As a consequence, all Altcoins will drop as well.
But, are all altcoins worthless?
If so, sell all your crypto.
If not, there will be a moment in time where altcoins will be no more linked to the value of bitcoin. And when that will happen we will have a mature market which will be no longer headed by hype, but by real value.
If Bitcoin has real value, it will continue to be exchanged with all the other altcoins and that will cause a raise in the value of both.
The question is:
Do you believe in Bitcoin?
YES: so you have nothing to worry about.
NO: blockchain will thrive nevertheless with other cryptocurrencies.