When you buy shares of a company at a dollar, and the share price is now two dollars, you definitely feel very happy.
Everyone wants to make money from investment.
The problem is that paper profit is meaningless.
You gain only when you sell.
There is no need to feel happy when you see the share price goes up, unless you want to sell it off immediately.
Paper profit is just a term to show that you can make money when you sell now.
If you hesitate, and the share price goes down to a dollar, you are not gaining or losing anything. That is why no need to feel happy when you have paper profit.
You feel happy only when the money is safely in your bank.