It is difficult to keep them knowing that you can have a lot of money now if you sell it. You can wait and double it when bitcoin hits a massive target. Its up to you actually.
I would suggest to keep them and if you see that bitcoin is rising don't sell them wait for it to rise even more.
It is difficult especially for those that have a big amount of bitcoin but Im sure that by now they have gotten used to the fact that they have an enormous amount of bitcoin and yet they are still living like normal people and not like the millionaires they are.
I am in very much favor of keeping Bitcoins for as long as one can. I think the way market price of Bitcoin is increasing with each passing day since the time of introduction of Bitcoin, there is no doubt to accept this fact that holding of Bitcoin is the most profitable thing as compared to any other thing. It involves minimum risk and greater profit.