Well for me..you can sell it in time that you think is beat to sell.if you think you gain already and you really need to sell why not..I believe also that you can keep it also until you get a higher price for bitcoin. 3 yrs ago bitcoin only in our country line for hundred thousand only but now already reach in a million for one bitcoin.this is really amazing.so keeping bitcoin wont you losse because keeping bitcoin is really a big investment for real.and if it has a taxes accept it because it is a part of the law implenting in your country.as long as you know you earned why not selling bitcoin.but still you are the one who decide of this.