I guess it depends on what your goals are. If you want to invest your money, then buy and hold is a good idea. If you want to trade then actively buying and selling is a good idea. If you want to actually use bitcoin, then transacting with it (selling) is a good idea. Everyone has their own reason.
I think for the bitcoin, it is better to hold for the long term as the price will rise a lot in the future.
Yes, the fate of bitcoins totally depends on the user and varies person to person. If you are a person with calm nature and are not in the need of money on urgent basis, for you it is good to hold onto bitcoins and become the new millionaire. But if you need money on weekly basis, do trading.