I sell the alts if it is obvious that the price will fall, and wait for the moment when it will be possible to buy at a lower price. The strategy of "sitting and waiting" is working quite differently, now you need to develop and take action, so as not to stay with an empty pocket
Only sell those coins which not having a very bright future, but just try to keep more and more altcoin with a proper development progress and it will give a huge possibility for us to get a lot of advantages from there in the future.