1. Invest for the long term and stick to it
If we make a graph of the stock markets and dive into the distant past, it seems they have only gone up. It may seem that way, but it wasn’t. There were huge dips in between. 
In 2007 – 2009, during the financial crisis, the broad U.S. stock market lost 57% in value. And in 2013, almost 5½ years later, prices were back at the same level.  And from the recovery in 2013 to mid-2025, the price has more than quadrupled (+ 300%), which is a growth of 12% per year.
What do we learn from all these movements and figures? We learn that investing for the long term is the best strategy. For stocks, that’s preferably ten years or longer. This applies when prices fall, and it applies when prices rise.  
When things are bad, you give it time to recover. This might take a few years, but it’s better to wait until 2013 than to take your losses in panic in 2009. And when things are good, you give it time for further growth. That 12% over 12 years between 2013 and 2025 doesn’t yield 12% * 12 = 144% profit, but 300%. This is because the 12% return from the first year also generates 12% in the second year, and so on. That’s how you end up with 300% profit after 12 years. This is the effect of compound returns.      
If you look through the peaks and troughs, you’ll see that the average return of a global stock portfolio has been around 8% per year over the past decades.