Costs and expenses matter. There is a good deal of argument among investors over this one. Many of them say that it makes no difference what you pay in fees for a mutual fund or to trade stock, as long as you get superior performance. Nonsense, I say. Performance is unpredictable.
Fees are very predictable.
Be a disciplined saver. Over my 25 years as a business journalist, I've written hundreds of stories about investors, successful and unsuccessful. The successful ones had discipline. They eventually realized that bonds weren't the best choice for long-term investors. The fund went nowhere for a decade, and in the early 1970s, they switched to a large-company stock fund.