Ask yourself is 10-20% daily increase in BTC sustainable? Does BTC have a superior technology compared to the various competitors in the market that could justify these gains? If you are not able to answer yes to these questions then perhaps this could be a trend that is coursed by FOMO. This is unsustainable both long-term and short-term.

Everytime you sell an altcoin in the XXX/BTC pairings then you are adding fuel to the fire.

Buying altcoins now however could end up in a long-term hold though so be prepared for that.