I haven't sold my bitcoins yet as its an long term investment for me but I do trade with different altcoins and I sell them when I am in a good position and have decent profits from it as I don't believe in holding altcoins longer as it can be very risky and may bring loss for me.
Good way for long term trading once you know you at least don't need it instantly as that can definitely hold down your coin. That was the reason I mentioned once that everyone knows what works best for them so it is best to stick to that, practice it well to make good decisions. However, it is best for you to follow the news at times instead of just buying in dips thinking everything is alright. Some coins can experience huge dips when they want to be delisted from the exchange and that my brother, can be a huge loss for you.