When you are confident that if you do full time cryptocurrency you will achieve success why not? if you are good trading or atleast you have some money to start mining why not? but if you dont have any of these,i wouldnt recommend you to do that because you could lose everything in just one wrong move in the market.
The answer would really depend on you. If you are financially stable and dont need to get a job to sustain your financial needs monthly, maybe it is okay to do cryptocurrency full time. But before you make a decision, you have to consider all things first and make sure that you are already a knowledgeable trader since crypto world is very unpredictable. Consider all things first so you wont regret in the end.