We know altcoins are a assets and when the money is needed people sell those assets at the exact moment. Since this is a wealth, so people sell it for their needs and there may be many reasons for selling it. If you know about cryptocarrency, then you can understand when the market is down, at that moment most people sell their coins for fear. If you have lots of coin and if you see market is doing down then there is nothing to worry about for a while or wait for some time. Market will definitely go to good position and you can sell your assets at a good price.