Now a days we sometimes seeing the price of Bitcoin falling along with others also falling.
At that time if I have Bitcoin then what should I do ?
Should I sell or hold?
This strategy will depend on the kind of person you are and what you're trying to accomplish, for example selling at the very top of the market was a very good choice when the price was close to 20000, you could have sold for fiat or for tether and then wait for the market to reach the bottom as it has already done and then buy again, if you did that you could have tripled the amount of bitcoin that you hold.