Your portfolio value depends on:
1. Your investment strategies.
2. Risk appetite.
3. And portfolio diversification.
Your stock values will fluctuate up and down, it is highly unlikely that your entire portfolio would be “zero”, unlike CFD trading, this would mean all the companies you have invested in were bankrupt. Additional protection can be added to your investments by using a “stop loss” and “take profit” on your positions, to maximize profits and minimize losses.