I had two wake up calls - strangely enough both were health related.
The first came when I was 12 or so and broke my leg. We just moved to the US a few month earlier and didn't have any kind of an insurance. I still remember what a financial burden that 25K hospital bill was and how long it took to pay off.
The real wake-up call came about 3 years ago when my grandmother had a heart valve replacement surgery. The surgery itself was covered by the insurance, but her insurance would only pay for a regular hospital room (a double) for the week or so that she needed to spend in the hospital after the surgery. It was great knowing that I was just able to pay the extra $200-$300 a night for a private room for her without even giving it a second thought. It was even better knowing that I could be there whenever needed without having to ask for time-off from anyone. Either myself, my parents or my grandfather were there 24/7 and it might have even helped her to recover a bit faster as she was able to leave the hospital two days earlier then originally expected.