The thought of burying one of my children
+1,000,000
When I saw a single guy I worked remotely as an exploration geologist, flew in a lot of small planes, drove (generally by myself) through various Australian deserts on a daily basis... and I felt bullet proof. Pretty well fearless.
Then I got married...
Then I had kids...
Having said that, these things don't keep me up at night. Conflict at work, looming deadlines etc does occasionally keep me up.
I now live in a country where pharmaceuticals are sold without prescriptions. If the pharmacy has it, it will sell it to you. Consequently, frequent travelers will often stock up on sleeping tablets etc whilst they're here. I'm a fan of knocking myself out on overnight flights so I can get the most out of my first few days where ever it is I'm going.
Recently my in-laws came over to stay with us, en masse, for three weeks or so. I was in HELL. I stopped coming home from the office... and it was obvious. I needed to do something to get me through this period. I asked a local doctor over a drink about my situation and he recommended a low dosage of Xanax.
I bought enough for the remaining days of their trip and I took one every day on my way home from work. It worked a treat. I sat together with everyone each evening after that and never once felt the urge to club a relative to death.
Wife was happy, I was happy, relatives think I like them.