The existence of blind spots is no secret, of course. But we can run into significant problems when we find somebody who's good at one thing and we start relying on that person for everything.
Bogle, who I admire for his pioneering index funds and the company he started (The Vanguard Group), is a case in point.
He knows indexing inside out. But I'm not sure I would go to him for a financial plan. And I doubt that I'd rely on him to help me build a portfolio of index funds to maximize my unit of return per unit of risk.
To my mind, Bogle and most of the advisors at The Vanguard Group often take the easy way out and counsel individual investors to focus on only a few of the great Vanguard index funds.
They may say you'll be just fine with a total market fund, for example, and that you don't need to bother with their more specialized offerings like small-cap value and large-cap value.
This is akin to a chef at a fancy food market telling customers to ignore most of the ingredients offered for sale and instead suggesting they buy a ready-made mix. That's probably fine if your goal is only to fix something that's "good enough." But if that's what you're recommending, what's the point of having a store full of intriguing ingredients?
Back to investing: For asset allocation help, I would much sooner rely on the writings of Larry Swedroe than those of Bogle. But I wouldn't go to Swedroe for tax advice. Unless your situation is pretty simple, there's no substitute for a good CPA.
I'm not a fan at all of investing in individual stocks. But I must admit that Warren Buffett has been very successful at picking value stocks. But I wouldn't even think of asking him for help putting together a balanced portfolio or an overall financial plan.
If you're looking for some good overall financial planning advice, it's quite possible that your uncle or your neighbor can steer you in the right direction. For that matter, I could do that and so could Buffett or Bogle.
But when you need to be sure you've got it right, there is just no substitute for somebody who has studied investing, insurance, taxes, retirement planning and estate planning — and who knows how to work with experts to put together a plan with parts that all work well together.
That, by the way, is the description of a certified financial planner, somebody who knows enough to get the experts all working in the right direction for a particular client.
Why am I bringing all this up? If I had my way, I would want every investor to have an ethical, competent experienced expert guiding them through the process. Most investors don't take the time to find that person.
One huge task for you as an investor is to learn to tell the difference between the courtship of campaign promises and the reality of competence or incompetence. Otherwise, your results may be the result of a series of random events.
My advice is to pick your advisors carefully and thoughtfully. Look for demonstrated track records. You don't have to have the "perfect" advisor. But you should have one who is legally committed to putting your interests first and who has demonstrated an ability to do so effectively.
Or, to get back to real life, when your bike "won't work," competent help might be closer and handier than you think.
For more on choosing the right advisor and getting the most value from your choice, check out my free e-book , "Get Smart or Get Screwed."
For the same low price (nothing), you can learn even more from my latest podcast, "How to beat the market, select an advisor and much more."
Richard Buck contributed to this article .