Selling is not a good thing and another fact is that with selling you are just making a little bit of profit, you can better wait on better prices to sell your bitcoin for.
Also the fact that the bitcoin can become the currency of the future makes it for me pretty simple that we should hold it.
But, if you have made money trading, mining or whatever with Bitcoin, you can also sell them and invest in other websites, businesses or start your own. Guys on localbitcoins and Paxful sell a single BTC for 150% its value. Loan sites can return 125% on the investment and who knows where your own idea will go if you fuel it with the money you made from Bitcoins.
Well, for sure we have different ideas we can do with our bitcoin, I have invested online and also use my earnings in the real life, I build a little store as our business and that alone already gives us a good income in a daily basis, I guess even how small your money but if you have the skills to grow it you would achieve your goal.