Depends on your money in this moment. When you have nothing to eat better to sell your coins you know 
In other cases just look for profit it comes with experience.
No, you should sell your coin mined when you have chance to sell it at good price. Example you waited a long time to sell your coin at high price when the price of which coin you mined just decreases everyday. And someday, you need money for urgent case, it makes you must to sell your coin at lower price instead of the time you can sell that coin at higher price many much at this time. In other cases just look for profit it comes with experience.