Buy when there is despair and all hope is lose.
Sell when everyone is buying and think bitcoin is the future.
Well said. Even though there are no strong fundamental indicators for bitcoin other than the long term economic nature of the currency, I generally try to buy "cheap" and sell when it is "expensive." I define this mostly based on sentiment. When the crowd is overexuberant, sell. When the crowd is irrationally fearful, buy.