I actually find the Bitcoin Greed and Fear index to be quite interesting... but I do believe that one need to be wise. Those who sold the fear in the start of 2018 still did good doing so, if they just set aside the money and kept them to 2020. In other words, if you sell with a plan (and don't sell all which might cause big regrets later), then that might not be a stupid thing to do.

But, once again - if you sell with a plan, then it probably isn't called panic-selling anymore!