What can happen if you don't choose the best keywords?

If you target the wrong keywords, you will lose a lot of time and you will lose a lot of sales.

You will invest a lot of time in optimizing your web pages for keywords for which your website cannot get high rankings at this time. Or you will invest a lot of time in optimizing your web pages for keywords that don't convert to sales. In both cases, you won't get much sales.
 
It is very important that you choose the right keywords that lead to high search engine rankings and sales. Make sure that you choose the correct keyword type.