You should:

Fear of being among the weak hands
Fear having not much information about Bitcoin
Fear of not having trust in the Bitcoin market
Fear that you will chicken out the moment the Bitcoin price plummet.
Fear that you don't have enough patience to wait for the next bull run and new ATH of BTC.
Fear that you would listen to all the FUD and negative sentiments of Banks and Anti-Bitcoin groups

In short, there is nothing to fear as long as you have patience and trust to what you are investing.