Do you regret it ?
or do you believe BTC will create a new ATH ?
I have never regretted that I did not sell my bitcoin in January 2018 ago ... because I still believe that at the beginning of January 2019 the price of bitcoin will exceed the price in January 2018 ago ... and I am ready to accept all the risks.
Even some people maybe regret, like what you said it is better to believe bitcoin will reach new ATH more than January 2018. And whatever price will up or down in future, is something that we will face.