What are the risks of investing in stocks & shares?
The price of stocks is a function of demand, which is based on investors' perception of the company's future earnings prospects.
Of course, until you sell your holding, these gains will not be realized. As an investor, you should assess your appetite for risk and, based on this, select the stocks with which you are comfortable.
Please remember: the value of investments may fall as well as rise and you may get back less than you originally invested.