If you are new to bitcoin you will fear something like these can happen. But don't get too emotionally bothered by downtrends, these are things normally occuring. If you really don't fear losing you can wait for years and see how  bitcoin will eventually go uptrend again. If you don't want to hold for long term then make a level for you to cut loses. For example you can set around 5 percent below of your buying price as your signal for selling to cut loses.