-Robert A. Heinlein
When it comes to finance you want to be the jack of all trades, not the master of one. Knowing how to do the financial engineering on a complex derivatives transaction, but not understanding why an adjustable rate for your mortgage is very bad and can be very dangerous to you and our financial system as a whole.
You don't need to know how to securitize a mortgage, but you do need to know everything that pertains to your personal mortgage. You don't need to know how to run a bank, but you do need to know how to balance your checkbook. You don't need to know how to do your taxes, but you do need to understand everything that your CPA says to you and then be able to ask poignant questions.
The same probably goes for your health. Knowing everything there is about skin cancer doesn't help you when it comes to detecting ball cancer. However, your best bet is to know how to identify both as early as possible and let the specialist do their best to treat you. While your finances are not a matter of life or death, always go by this simple axiom: if you don't understand it, don't do it.