What has a very low cost, but could have a major reward (or save you from disaster)? This should be thought of in terms of any of your resources (most importantly, your time, money, and energy).
For example, buckling your seatbelt takes two seconds, but it can save your life (or save you from an expensive ticket). The reward (living and/or saving money) seems to be well worth the cost (a few seconds).
Where can you find these asymmetric risks in life? Whenever you find them, make sure you take advantage of it.