Selling bitcoin would only be wise when you really need money. Having bitcoin is having a good kind of asset, there is no like bitcoin that can appreciate in value at an instant. As long as you can keep your bitcoin at any cost, it is the wisest thing to do. Prefer to hold tha to spend it, in no time.you will see the fruit of your waiting and investment.
Yes waiting for a longer time and not to sell our coins is a good idea but if someone will need for any emergency then they can.
There are many people who also sell their coins when they feel that now they will not see the price rising again, actually they do not know about the coming future of bitcoin and they do not know that the adoption of bitcoin is increasing more faster and the price will also increase like that.