“An investment operation is one which, upon thorough analysis, promises safety of principal and an adequate return. Operations not meeting these requirements are speculative.” -- Benjamin Graham
One of the biggest mistakes investors can make is not understanding the business they're buying into. As the godfather of value investing, Benjamin Graham tried to teach the world, a share is part of a business, it's not a lottery ticket. Would you buy a coffee shop hoping to flip it at a higher price without looking at the company, understanding how it works and if it's profitable? Of course not, so why would you do the same with a share?

