It is wise to hold Bitcoin 99% of the time during a bull bear cycle. There is only a 1% chance that the altcoin/BTC exchange rate will experience a dead cat jump, and then continue to follow an indefinite zero exchange rate pattern. For example, ETH/BTC, DOGE/BTC, LTC/BTC, XRP/BTC. Currently, the XRP/BTC exchange rate is still relatively high, and it is possible to sell all XRP for Bitcoin (the first reminder was in January).