Let's say I am spending 250 USD to mine a coin of worth 330 USD, selling it immediately doesn't give me a big profit. If I am selling the same coin for 500 USD then thats a good strategy.
(amount spent on mining per coin in FIAT) : (Value of the coin)
when you get a good ratio convert the coin to FIAT.
You should almost always meet your genuine unsurety about selling a coin with a 50/50 trade. If your balance is 1000 X coins and you want/need to sell, but you have a lot of doubts, then try selling 50% of them, or 500 coins and go from there. You may be selling because of price changes up or down.