To sell or hold altcoin is very difficult to say. But it is even harder to predict market growth. Therefore, it is everyone has to decide for itself. Tips already given a lot. Listen to the voice of reason!
It will depend on what we have, to sell is for those who are not getting active or focused by the team for improvements it might goes lower even the market recovers, to hold is those for team that are strong enough to try things to workout their project.