We all make mistakes in many areas of life. These mistakes are usually fairly harmless — we took a wrong turn while driving, used the wrong ingredients in a recipe and so on. But sometimes, our mistakes can be costly — especially those connected to investing.

Here are some of the most common investment mistakes:

• Too much buying and selling – some people find it exciting to constantly buy and sell investments in the pursuit of big gains. Yet, frequent trading can work against you in a couple of ways. First, it can be expensive — if you’re always buying and selling investments, you could rack...