You are quoting and following Warren Buffett, good for you if you believe you can use his style, he is not always right as no one is, he lost a fortune trying to trade silver, and also bought oil stocks at the peak, when oil was $140. He is a fundamentalist with unlimited capital and information available to him that is not available to the public, fundamental information is always already reflected in the price of a stock or commodity,you'll never have an edge by depending on fundamentals alone. The trader I learned everything I know from is different, I was trained by him,he is short term to intermediate term ,Victor Sperandeo, he started with a few thousand and turned it to a billion +$s , all trading his own money,not other people's money, and George Soros gave him Billions of $ to trade for him. Vic was dubbed by Soros as the trader of the century,inducted in the hall of fame, featured in the book Market Wizards and Super traders,WSJ called him the Ultimate Wall Street Pro, it will be worth your time to buy his 3 books and read them , while Buffett was long in 1987, Vic was on CNBC a week before the crash saying he is short up to the limit, and the market will crash.
I am not trying to start an argument, just wanted to explain there are different approaches to investing and trading, each needs to find what works for him. I trade everything from stocks, forex, commodities, long and short, I was never an investor, and I do extremely well. If index funds are your cup of tea, great, important is the end result.