It depends what you define as a "20% profit on your trade". As an altcoin trader, I see all profits as coins, not USD, but maybe youre only in the business of trading USD. When you say 20% profit, do you mean that the LSD/USD value went up 20% or that LSK/BTC value went up 20%?
If LSK/BTC went up 20%, then your 0.64BTC has increased to 0.768BTC. Multiple 0.768BTC by the BTC/USD and you have the USD value. If BTC/USD has remained the same since the time of your trade, then you have a 20% profit in USD as well. If BTC/USD dropped more than 20%, then you have a loss in USD (but not until you sell BTC/USD). If BTC/USD has increased, then you have have two different gains multiplied by eachother.
If LSK/USD went up 20%, then you need to know the price of BTC/USD to figure out how many bitcoins you have. If BTC/USD remained the same, then you have 20% more bitcoins. If BTC/USD fell, then you have two gains on your level of bitcoins. However, if BTC/USD has risen more than 20%, which happens quite often, then you have LOST bitcoins.
Yeah this one is good. This is all about you. If you have that much ability to hold as your patience allows you to, then better is to hold. It gives you much more than your expectations and you will be making incredible profits at the end. But day trading have vital role too. You can earn money at daily basis and can make your daily needs fulfil with handsome money. Still, choice is yours at the end.