FOMO can cause you to make some pitiful trading decisions. The hard thing to do is to take the risk that most people aren't, but thats where you will find the real profit - not going with the current market but going against it because of what you know is coming.
When everyone is buying it is often time to sell. If everyone is selling, it is often time to buy
It's true that as Bitcoin goes up the alts go down in general, but the influx of fiat into Bitcoin stands to benefit alts in the long run as a percentage of it will eventually end up in altcoins.
The rise of Bitcoin is good for altcoins.
The easy strategy is to HODL Bitcoin and alts, accumulate during dips.